The Devs are often in this forum so they will see this.
For the error:
Error is: “0x80070005, Zugriff verweigert” (EN: “0x80070005, access denied”)
I’m wondering if the file is being locked by Synology Drive during the write attempt. Or possibly some sort of race condition.
I think this is a helper utility that opens a file dialog. Check here for some information on this:
Try renaming the file, restart LightBurn, and see if you still have the issue with save.
Also review the portion about it possibly being stopped by Anti-virus programs. Don’t know if this applies in your case.
[EDIT] - forgot to answer about the logging. Help->Enable Debug Log. Should write to LightBurnLog.txt in Documents.