Hi and welcome to the forum,
I can describe you the way I was forcing the rescan.
I use Total Commander for a very long time. It is a very powerful file manager with roots on Windows 3.1 (or even older).
It is a shareware and is totally functional if downloaded and installed from here.
There are surely other similar file manager with similar functionalities.
After installing, navigate one panel to the root folder of your photos or a folder with photos, also containing subfolder is possible.
- Use Alt+F7 to open the search dialog. Here enter the pattern for the file name (e.g. *.xmp) and uncheck to look in compressed files. Start search by hitting Enter or with the button top right.
- After that, you have a list of files in the search window. In the botton row 2nd from right is “to window” or something similar (I use it in Hungarian), which brings this list with filename and path to the original panel.
- Here you select the files with * (asterix or “star”) on the numerical keyboard. Alternatively you can use the second menu “Selection”. This marks turns the marking of the files (when nothing was marked as default, it selects all files).
- Choose “File - Change attributes” (first menu item). Here you check the checkbox for changing date and time, there is a button for current and hit OK.
This changes the file modification date to the one set in the dialog.
Depending on the number of files and type of drive (hdd or ssd) this can take some seconds up to a minute or so.
- Mylio should recognize these changes, but you can force it with “Organize - Scan for changes”. It can take also some time until all the files are read and synchronized.
This is pretty much the functionality of touch, but without the command line (and Win10 doesn’t have touch by default).
Which file types do you have?
Mylio saves every change you made inside Mylio to the XMP sidecar files for every filetype.
Other programs might save changes to the JPG, DNG and TIFF files themselves (there might be other extensions, too). Most programs don’t touch RAW files (like CR2, NEF, ORF).
If you have smartphone photos (usually JPG) with GPS data with wrong display in Mylio, you might have to change the timestamp of those files, too. Reading these files takes considerable more time, then only the small XMP sidecars (but still much less, then your original process).
If you used also “Photo - Save metadata to file” in Mylio,then you have to change the timestamp of those files too.
My assumption is, that only data got corrupted, where the UI was active on the file or folder since 3.8, but using the Map view or Map tab on a folder can show you, if they are in the correct position.
Edit: I used this on my main computer which is configured as a vault. I guess you should use it on the original files, but if they are on an external drive, I don’t know how Mylio reacts for changes on those files, I have no experience.