@Gwen-Dragon When looking at the reports directory again today, I noticed that the earliest reports were now from May 1, so there definitely is some automatic culling done of the oldest files in that dir (I would suggest more than 2 days-worth be left in there--or at least maintain a log somewhere).
This means that I don't know when this started, since I seldom look there. It couldn't have been THAT long ago, but certainly possibly before 3.0.
So picking up on your extensions idea, I found through the process of elimination that it's caused by running both Google Docs Offline 1.10.0 and one other extension. Disabling one or the other works around the problem. Not sure it's worth reporting in that case. FWIW, it doesn't reproduce in Chrome 83.0.4103.34.
Update: Uninstalling/reinstalling Google Docs Offline seems to fix this issue.
Update 2: But it eventually recurs later.