Synchronization "stands still"

I've been trying to synchronize my vacation pictures from the iPad (LR) in LRC 13.4 for 2 days. I can see them all now, but the synchronization still says "481 photos are being synchronized".

In LR on the iPad & iPhone & in the browser the synchronization is complete or there is no longer a message. Recently I can no longer see which picture is “stuck”. I can only switch to WebLR. Where do I see the error now?

[Moved from ‘Bugs’ to ‘Discussions’ by moderator, according to forum rules. A ‘bug’ is not just another word for any problem with software!]