I have occasionally had problems with files not saving.
Today I have a specific example in case some dev people want to look at if: https://stock.adobe.com/579753145
The document seems to be plain eps (or maybe oldest Illustrator version ever).
When I open it in illustrator to just look at it, 27.5 on windows occasionally seems to keep some filehandle open (so I cannot make a change and "save as")
If that does not happen,, and I try to save, I get the "save as" dialogue, but in the end the file does not change. In detail: the documentAfterSave event is triggered in a CEP panel, and cep.fs.stat() returns current date for file modification. In reality, a new file with a gibberish name is created that cintains the actual edits.