I would need someone who knows more about this to verify, but could 8dot3 names be causing this issue?
I back up a file server that constantly has people deleting, adding, and editing files, and after turning off 8dot3 DOS names I have never had a problem since.
As far as I know, it’s a simple on/off switch for 8dot3 names; but I don’t know if C: will allow you turn off 8dot3.
fsutil 8dot3name set F: 1 (disable on selected volume)
or
fsutil 8dot3name set 1 (disable all)
May not be useful for the original question, but it might be for your most recent one @hippy1970 .