Hi,
this is a bug on current and on some older versions of LR.
1) have a LR on Windows 11 (NTFS) which contains directories with special characters in their names.
In this text I will use as an example directory named "Juraj Porträts", containing 58 pictures.
Other german special characters like "ü" or slovak "á" apply as well.
2) in the Folders panel, right click the folder "Juraj Porträts" and
do Export This Folder As A Catalogexport catalog
on ExFAT formatted USB-stick.
3) import it on macos (M1, APFS).
This works flawelessly.
4) edit pictures in LR, in Photoshop, delete them, save metadata in files.
This works flawelessly.
5) right-click on "Juraj Porträts" and pick "synchronise folder":
LR will suggest to "import new photos (58)" AND "remove missing photos from catalog (58)"
6) hit "synchronise".
58 photos will be removed from catalog and the very same 58 photos will be added to catalog.
7) Lightroom catalog will contain 2 (two) folders named "Juraj Porträts".
One of them is empty, the another one contains 58 photos.
This duplication only occurs in LR catalog, finder only shows one directory "Juraj Porträts".
8)remove the empty folder and click "synchronise folder" on the another one.
Now, LR will find no discrepancies.
9) it also might be worth noting, that you do can use special characters in folder names in LR on mac,
provided that you create them on mac.
This weird behaviour (6 and 7) only occures on folders imported from LR databes originating from Windows .
I have never tried the other direction (export on mac / import on Windows).
best regards from Linz, Austria