Lucie Eisenmayer 

Hi Lucie,

intermittent errors, the developer's nightmare... I can think of two things to try:

• run the converter by starting with extended debugging. using this script: C:\Program Files (x86)\SDL OpenExchange\Glossary Converter\GlossaryConverter_Debug.cmd 
  this will create an extra log file here: C:\Users\%USERNAME%\AppData\Local\SDL OpenExchange\GlossaryConverter\debugLog.txt
• delete or rename the settings file: C:\Users\%USERNAME%\AppData\Local\SDL OpenExchange\GlossaryConverter\settings.xml

Just to confirm: once the error happened, any conversion fails, even after a restart? And there is no log file created at all, in the location where your source file is? 

Thank you! I have actually just figured out (finally!) what the issue was. Apparently, Glossary Converter just didn't like where the file was stored (I'm guessing it might have to do something with OneDrive), even though it didn't have a problem before.
So I just copied it to the desktop and suddenly, it worked again. (And nope, no error message, no log file. Nothing.)

But I will for sure save your answer, it might come in handy next time there's an issue :).

Just for the benefit of anyone who reads this in the future: There are indeed problems if files are on a network drive, like OneDrive or \\mac drives. They only happen sometimes, and so far I could not reproduce or fix it. So, if you run into similar problems, try Lucie's fix and copy the data locally.