It's possible the DST shift could cause MC to do 'Update Library (from tags)' on some files. Also, I believe the issue has been fixed for good (it was related to strange DST handling in a Windows API for legacy reasons).
No, not an issue with DST -- our time change in France was 27/10 and had no problems. It was not shifted by an hour it was shifted by more than a month for almost all of the files. I know this because that is when I re-analyzed all my files (volume analysis) this summer. Also the file dates that were not changed and were all in august reflecting this. Maybe I wasn't clear but these "modifications" took around two hours to do looking at the time stamps.
What type of files?
only audio files - no folder.jpg or txt files (see attached screen shot)
However, this should not change the data modified. Could you test a manual 'Update Library (from tags)' and watch the date modified on the file system?
Well, the actual modification date was written to disk; I tested update library from tags like you suggested Matt, and there was no change to the file system. The only files that are changed are the audio files as you can see (see s.s.)
(or the first time you did a manual Auto Import after Nov 3).
THIS has something to do with it! I always manually 'autoimport". To test this I just ran autoimport manually again and 84 files were "modified" (date changed). Autoimport is updating files that I neither played nor retagged. These files were on my screen however.
For info, my "autoimport" config is only Update for external changes and Fix Broken Links. Most of my metadata fields are set to write to the file. (including import date^^)
Also, just ran it a third time and always see "analyzing files 1-8800" which appears after the scan of 90K files (see SS) ?
Has there been any messing around with the autoimport function recently? If so would keeping the tag window open open and then closing without making any changes be interpreted as a modification to the library? If so this would be a real drag, but it almost looks something like that is happening.