Please see https://forum.syncthing.net/t/some-deletions-and-modifications-getting-stuck-in-sync-since-v1-27-5/21893/17. You need to upgrade Syncthing to https://github.com/syncthing/syncthing/releases/tag/v1.27.6-rc.1, however this alone won’t fix the files that are already “stuck”.
As it seems that there are a lot of them in your case, I’d suggest that you simply remove and re-add the folder in Syncthing on each device. You can keep the actual files on the disk. Just make sure that all devices run v1.27.6-rc.1 before trying to do anything, as otherwise you will likely end up with new files getting stuck anyway.