I had exactly the same issue on two remote devices. On the remote end I had tried rescanning, touching the folder, recheckdbevery and eventually renamed the remote devices index folder, and still no joy.
in the end I renamed the receive only index folder and let it reindex everything. I know it’s not the ideal solution, however I had also tried recheckdbevery and it made no difference, however blowing away the local index I think it’s fine now. Certainly when I open the remote device out of sync items, i’m now getting items, where before it was blank like tomasz.
As a thought, could it be that over the various upgrades, the index db simply is getting messed up internally and a wipe and restart clears out any issues?