How to remove out of sync issues

I have three peers A, B (untrusted, encrypted), C. I delete a large file 600 MB from A and C almost simultaneously. B stays permanently out of sync with all peers, stuck at 95%.

Clicking on the out of sync items in GUI shows the deleted file with size 0 bytes (it shows as an encrypted file in B, and plaintext in A and C). However, the file indicated in GUI does not exit in the folder in A and C. The encrypted file does not exit in B either; its empty folder remains which is also deleted after B is restarted.

I reproduced this issue several times, and the same problem is encountered.

Last time, I had to delete the database on B and force it to regenerate the database.

Why does this happen, and how to prevent it??

Peer B is an untrusted always-on node in the cloud. For example, peer D that is also connected to A and B, and is not encrypted, doesn’t encounter this issue. The file gets deleted there.

Peer C is the beta iOS app Synctarian.

I added the same file back to A, and while it syncs to B, it stucks at 32% with B.

I created an empty file with the file name indicated in B GUI. That solved the issue at B, but not at A.

Unclear; it should just be deleted on B as well.

I updated the post. Any idea?

There seems to be a dangling reference to the file left, either in database or only in GUI. Any way to ask Syncthing: forget about this item and update the database?

Can you post screenshots of the Syncthing Web GUI from all affected devices?