Changing names with Rename window through RegExp and 'Last names change' - modifies the 'modified' date of a file or files. A bug or this is intended so? I am sure that it happens not always. It should not be this way - rename is not an modification, and when photos are ordered by 'modified' - this changes the order.
Just renaming doesn't change a file's date, unless it is moved across drives, modified by e.g. a complex rename script, or is modified by a third party component which may monitor for new files, or similar.
What kind of file are you seeing this with?
It happens when I rename simple photos (without moving them). I select photo (or photos), open Rename window with shortcut (F4), choose the "Last changed name" and there is already this in old name: (IMG_|MVI_|DSC|-01_)(.*) and in the new name: name_\2. After pressing Enter the 'modified' date is changed. And this not always - I could not find more details about the 'constellation' in which it happens and in which not. It has never happened when I did the same with TotalCommander.
I have checked - it happens even with simple rename (without window). So it happens with every Rename.
Does it only happen with photos or video files? What about a simple text file?
I could not check it know - now Rename is working ok with all files (does not change any date). I have not run or stopped any additional program (just normal usage I do), nor make the reset. Strange thing - like Doctor Jekyll and Mr Hyde... Could it have to do with low system memory? (but from a moment with almost the same memory it worked again well). I will observe this.
Again - Rename changes only photos modified date - not films, not texts - only photos. (After reset with a lot of free system memory). It happens after some previous successful rename of photos without change.
How are you renaming the files?
Are you using any rename scripts?
Does the problem only happen when in thumbnails mode, and/or with the viewer pane open?
For example, it's possible a bad shell extension is modifying image files whenever Opus asks it to do what should be a read-only operation, like extracting the thumbnail data or details for a column in the file display.
Another possibility is search/indexing software, or cloud storage/synching software, which may be detecting and modifying new files.
If you're familiar with Process Monitor, it could be used to find out which process is opening the files to modify them. (Finding an event where one of the files was modified, then right-clicking the an event and choosing the Stack option will also show which DLLs are involved, in case it is a shell extension or similar.)
It could also be interesting to store a copy of the original file, then rename it, and then compare the two files (or upload them for us to compare) to see if anything was changed other than the timestamp itself. e.g. Something could be generating embedded thumbnails or modifying EXIF tags automatically, for some reason.