Hi Mathias,
first of all, great tool! I found it this week when setting up my new computer. I was not satisfied with any previous free/open-source Commander-style tools that I tried. Yours is already pretty great with a lot of features and configuration options and I see great potential in your extenstion system.
Now about the bug I found:
When using the tool "Tools / File Checksum / Calculate checksum value from file" the dialog "Calculate Checksum Value" opens but immediately crashes (before displaying any calculation progress)
IF I use German as language. Otherwise the tool works fine.
Verified working in: English, Italian, Spanish, Chinese (simplified), French
Best regards