One possible explanation is that at least one of your fields was updated and written to the file as a new tag value. That causes the operating system file date to change and MC may then re-import it if the folder is being watched. In your screenshot, "Date Modified" looks like MC library data. Does it agree with current operating system date for this file? However, it's also interesting that your "Date Tagged" field is empty. Has this version of the file ever been seen and tagged by MC before? Which tags does it contain (look at Action Window > Tags > Tag Dump)?
You can see a list of all fields that could possibly be written to the file with: Tools > Options > Manage Library Fields > Library & Folders > Show only fields saved in tags. You can uncheck the box "Save in file tags (when possible)" for any of these fields you are actually using, which in principle should avoid the tag update file issue in the future.
If you have copies of both the original file (say from a backup drive) and the recently imported file, then a binary file compare is a great way to look into the files and see exactly what has changed. For example, the program Beyond Compare (BC) does an excellent job of this, at least for flac files. It clearly identifies the tags at the top of the files and shows them side-by-side in human-readable text separately from the binary music data which follows. I have never seen changes in the music data - it is always the fields which change. Sometimes their values are the same but they have been re-ordered. This will also be evident.
Have you selected Tools > Options > General > Importing & Tagging > [ ] Automatically import files when played, and then played the file from a different source?
Another challenging issue is when the Windows file "Date modified" mysteriously changes and BC shows the old and new files are binary identical! This wrecks havoc with file synchronization/backups based on file dates. I see this occasionally (maybe 1-2 times a month), always for whole music albums (all tracks updated to the same new "Date modified" timestamp, while sidecar files and folder dates are unchanged), multiple albums at a time, and often the same albums. I'm in the process of tracking this behavior more carefully and will open a separate post when I have more definitive information (unless anyone can explain the puzzler now!).
Correction: I do not mean to imply that simply updating tags always results in changing the import date. Normally that should not happen.