If just one file is selected, behavior is in part as expected: foobar2000 is launched, a single file shows up in the playlist but... it doesn't start playing (like in Explorer).
Is the info below what you need?
2020-07-27 12:31:01.455 [7256] (view=000001E890A94390) BrowsePath requested : 0000000000000000 = M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman\
2020-07-27 12:31:01.455 [7256] Parent FileItem is invalid, FileSystem volume scan is required
2020-07-27 12:31:01.455 [7256] FileItem - UpdateLock ON : 000001E89157ABC0 = 'M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman'
2020-07-27 12:31:01.455 [7256] ThreadWorkManager [Icon] - Request STOP - Current state : Stopped
2020-07-27 12:31:01.455 [7256] The Main Async FileSystem Scanner thread manager is created!
2020-07-27 12:31:01.455 [7256] File System Scanning Thread - Creating new Thread! (ThreadID : 7708) (AutoDelete : 0)
2020-07-27 12:31:01.455 [7256] File System Scanning Thread Resumed (Thread ID: 7708)!
2020-07-27 12:31:01.455 [7256] Leaving BrowsePath - Will wait for scan to complete (If scan was started)
2020-07-27 12:31:01.455 [7708] File System Scanning Thread - Started.
2020-07-27 12:31:01.455 [7708] Init FileSystem Scanning of path : M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman\
2020-07-27 12:31:01.456 [7708] FileSystem Volume Scanning started : 000001E89157ABC0 = M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman
2020-07-27 12:31:01.574 [7256] (view=000001E890B25780) BrowsePath requested : 0000000000000000 = C:\
2020-07-27 12:31:01.575 [7256] FileItem have NeedRescan flag set : 'C:'
2020-07-27 12:31:01.575 [7256] Filesystem volume scan is required : 'C:'
2020-07-27 12:31:01.575 [7256] FileItem - UpdateLock ON : 000001E8914026D0 = 'C:'
2020-07-27 12:31:01.575 [7256] ThreadWorkManager [Icon] - Request STOP - Current state : Stopped
2020-07-27 12:31:01.575 [7256] NEW FileExplorer Thread will be started.!
2020-07-27 12:31:01.575 [7256] File System Scanning Thread - Creating new Thread! (ThreadID : 9152) (AutoDelete : 1)
2020-07-27 12:31:01.575 [7256] File System Scanning Thread Resumed (Thread ID: 9152)!
2020-07-27 12:31:01.575 [7256] Leaving BrowsePath - Will wait for scan to complete (If scan was started)
2020-07-27 12:31:01.575 [9152] File System Scanning Thread - Started.
2020-07-27 12:31:01.576 [9152] Init FileSystem Scanning of path : C:
2020-07-27 12:31:01.576 [9152] FileSystem Volume Scanning started : 000001E8914026D0 = C:
2020-07-27 12:31:01.576 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute '$Recycle.Bin'
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Found item '$WINDOWS.~BT' 0x00002010
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute '$Windows.~WS'
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Found item 'AMD' 0x00002010
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Found item 'Arquivos de Programas RFB' 0x00002010
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'bootTel.dat'
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'Config.Msi'
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Found item 'ContaCam' 0x00002010
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Found item 'dados' 0x00002010
2020-07-27 12:31:01.578 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'Documents and Settings'
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Ember Media Manager' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'ESD' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'inetpub' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Intel' 0x00002810
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'lin2win' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'loggger' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Logs' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'MSOCache'
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'netuptime' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'OneDriveTemp'
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'pagefile.sys'
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'PerfLogs' 0x00000010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'PRIME-A320M-A-ASUS-5007' 0x00000010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Program Files' 0x00000011
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Program Files (x86)' 0x00000011
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'ProgramData'
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Progs' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Python27' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'Recovery'
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Sandbox' 0x00002011
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Sardelli' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'script.speedtestnet-10.0.0.zip' 0x00002020
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'swapfile.sys'
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Exlucde item Hidden/System attribute 'System Volume Information'
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Temp' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Users' 0x00000011
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item 'Windows' 0x00000010
2020-07-27 12:31:01.579 [9152] FileSystem Scanner : Found item '_DL' 0x00002010
2020-07-27 12:31:01.579 [9152] FileSystem Volume Scanning completed
2020-07-27 12:31:01.579 [9152] FileItemsCache needs to be updated. ( Removed : 0 , Existing : 26 )
2020-07-27 12:31:01.579 [9152] FileSystem scannig process completed
2020-07-27 12:31:01.579 [9152] File System Scanning Thread - AutoDelete - Deleting and exit thread
2020-07-27 12:31:01.663 [7708] FileSystem Scanner : Found item '..' 0x00002010
2020-07-27 12:31:01.663 [7708] FileSystem Scanner : Found item '01 Quintet with piano n.1 ¬I. Moderato molto espressivo - Allegro.flac' 0x00002020
2020-07-27 12:31:01.663 [7708] FileSystem Scanner : Found item '02 ¬II. Presto.flac' 0x00002020
2020-07-27 12:31:01.663 [7708] FileSystem Scanner : Found item '03 ¬III. Grave.flac' 0x00002020
2020-07-27 12:31:01.663 [7708] FileSystem Scanner : Found item '04 ¬IV. Con passione.flac' 0x00002020
2020-07-27 12:31:01.663 [7708] FileSystem Scanner : Found item '05 Sonata for piano n.2 ¬I. Maestoso - Agitato.flac' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item '06 ¬II. Largo.flac' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item '07 ¬III. Toccata. Vivo.flac' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item '08 Quintet with piano n.2 ¬I. Moderato - Allegro.flac' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item '09 ¬II. Larghetto.flac' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item '10 ¬III. Allegro giocoso.flac' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item '917QyK1bOPL._SL1500_.jpg' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item '91v-rCMQ-UL._SL1500_.jpg' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item 'A1fMj6epVtL._SL1500_.jpg' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item 'bacewicz.txt' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item 'back.jpg' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Scanner : Found item 'front.jpg' 0x00002020
2020-07-27 12:31:01.664 [7708] FileSystem Volume Scanning completed
2020-07-27 12:31:01.664 [7708] FileItemsCache needs to be updated. ( Removed : 0 , Existing : 17 )
2020-07-27 12:31:01.664 [7708] FileSystem scannig process completed
2020-07-27 12:31:01.664 [7708] File System Scanning Thread done - Will wait for next scan job (7708)
2020-07-27 12:31:01.882 [7256] Update of BrowseCache started ( parent : C: , Valid : 26 , Removed : 0 , New 26 )
2020-07-27 12:31:01.882 [7256] Update BrowseCache in all views that caches path : (000001E8914026D0) = C:
2020-07-27 12:31:01.882 [7256] (view=000001E890B25780) Insert items into View BrowseCache : Items in Cache : 0, Items to Add : 26, Cache for path : C:
2020-07-27 12:31:01.883 [7256] (view=000001E890B25780) Insert from BrowseCache into VIEW - Existing Items : 0 , Items to Add : 26, Cache for path : C:
2020-07-27 12:31:01.889 [7256] Background Thread - Start Job ( JobName : Icon Extractor , CMD : Cmd_None , CurrentState : Stopped)
2020-07-27 12:31:01.889 [7256] Background Thread - Start - Thread state is STOPPED. Queueing job
2020-07-27 12:31:01.889 [7256] FileSystem Scanning and Caches and UI update completed
2020-07-27 12:31:01.889 [17576] Background Thread [Icon Extractor] - Starting
2020-07-27 12:31:01.889 [17576] Icon Extractor - Begin
2020-07-27 12:31:01.894 [7256] FileItem - UpdateLock OFF : 000001E8914026D0 =' C:'
2020-07-27 12:31:01.899 [7256] Update of BrowseCache started ( parent : M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman , Valid : 17 , Removed : 0 , New 17 )
2020-07-27 12:31:01.899 [7256] Update BrowseCache in all views that caches path : (000001E89157ABC0) = M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman
2020-07-27 12:31:01.900 [7256] (view=000001E890A94390) Insert items into View BrowseCache : Items in Cache : 0, Items to Add : 17, Cache for path : M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman
2020-07-27 12:31:01.900 [7256] (view=000001E890A94390) Insert from BrowseCache into VIEW - Existing Items : 0 , Items to Add : 17, Cache for path : M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman
2020-07-27 12:31:01.901 [7256] Background Thread - Start Job ( JobName : Icon Extractor , CMD : Cmd_None , CurrentState : Running)
2020-07-27 12:31:01.901 [7256] FileSystem Scanning and Caches and UI update completed
2020-07-27 12:31:01.904 [17576] Icon Extractor - Done - 26 icons changed
2020-07-27 12:31:01.904 [17576] Icon Extractor - Begin
2020-07-27 12:31:01.906 [7256] FileItem - UpdateLock OFF : 000001E89157ABC0 =' M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman'
2020-07-27 12:31:01.933 [7256] OnChangeEvent - View : 000001E890B25780 - Event : 'Icon Changed' - FileItem 000001E8914026D0
2020-07-27 12:31:01.935 [7256] OnChangeEvent - View : 000001E890B25780 - Event : 'Icon Changed' - FileItem 000001E8914026D0
2020-07-27 12:31:02.221 [17576] Icon Extractor - Done - 0 icons changed
2020-07-27 12:31:02.259 [17576] Icon Extractor - Begin
2020-07-27 12:31:02.263 [17576] Icon Extractor - Done - 16 icons changed
2020-07-27 12:31:02.263 [17576] Icon Extractor - Begin
2020-07-27 12:31:02.263 [7256] OnChangeEvent - View : 000001E890A94390 - Event : 'Icon Changed' - FileItem 000001E89157ABC0
2020-07-27 12:31:02.264 [7256] OnChangeEvent - View : 000001E890A94390 - Event : 'Icon Changed' - FileItem 000001E89157ABC0
2020-07-27 12:31:02.288 [7256] Start Monitor folder for changes : C:\ ( Add Count : 1)
2020-07-27 12:31:02.293 [7256] Path is now monitored : C:\ ( RefCount : 1 )
2020-07-27 12:31:02.293 [7256] Start Monitor folder for changes : M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman ( Add Count : 1)
2020-07-27 12:31:02.293 [7256] Path is now monitored : M:\MUSICm\&\B\Bacewicz=Sonata for piano n.2; Quintet with piano n.1; 2 ~Krystian Zimerman ( RefCount : 1 )
2020-07-27 12:31:02.469 [17576] Icon Extractor - Done - 0 icons changed
2020-07-27 12:31:02.470 [17576] Background Thread - Work finished or stopped (Signaled : 0)
2020-07-27 12:31:02.470 [17576] _WorkerThreadProc - Jobb Name : Icon Extractor , Thread Jobb State : Stopped
p.s. Just for the record: most (not all) other multipane file explorers do have problems emulating the usual File Explorer behavior for multiple selected files associated with an application.