@tomasz86 Please see https://forum.syncthing.net/t/unexpected-items-on-remote-untrusted-rpi3
Your issue is very similar and maybe a duplicate of the issues I have been reporting for my encrypted folder(s). Essentially, my problem occurs because the modtime is not correctly changed on some modified files on the encrypted side. My experiments with a parallel unencrypted folder using rsync is evidence of the modtime difference. Reverting the changes (/rest/db/revert) ensures files are in sync and the Unexpected Items are deleted. See Simon’s bug report at https://github.com/syncthing/syncthing/issues/7991