I had in parallel similar problem with between Laptop #1 and Server #2, and between Workstation and Server #1.
I finally solved the first problem by connecting Server #1 and #2 through a SSH tunnel and letting them sync. The second problem I solved by “un-ignoring” the problematic folder on Workstation letting it sync. After all the syncs were finished I ignored the problematic folder again.
There was also a persistent “failed items” issue at Server #1, but all those files were deleted in all the computers already. For reasons unknown to me, Syncthing did not clear out this situation on its own (over several hours) so I sorted out that (unrelated) issue by forcing resync.
Now everything is in sync, but I still think the out-of-sync items never competing was caused by a bug in Syncthing code. I will continue to keep the servers connected with help of an autossh tunnel (ran as systemd service).
Quite a lot of work 