What became of below experiments from last time you had the same problem? Nobody else is seeing it.
I’m also still looking for lines from a verbose log for one of the affected files, as shown here with example.
If you have some extra space, how about replicating it (in whole or in part) to see if fresh backup hits this?
If it does, it supports the version theory, although comparing code for 2.0.5.108 didn’t see obvious change.
EDIT: More accurately, it supports not doing the delete and recreate until the cause of the issue is located.
Metadata was reported as not changed, but still requires being added? was a 2018 regression caused by code change. This got a lot of debugging experiments. You can read them and see if they help your issue.
In case this is due to the options used, could you post a redacted version from Export As Command-line?