It’s most likely the (new?) dreadful Windows Ransomware protection thingy. Solved in Rack 2.0.4. But I see you’re running 2.0.4 so that’s strange. Have a look at the attributes of the …/Documents/Rack2/ directory. Is it read-only? If yes that’s the Ransomware Protection, but Rack should have been added to the exclude list. If it didn’t work you might have to make the directories under …/Documents/Rack2/ writable manually.
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