syncthing sync is hung

I set syncthing a couple of months ago and had no problem syncing 3 folders from my computer and android device to each other. Both devices can send and receive. But this happened first time yesterday. I had a new file in one of the three synced folder at my computer and wanted to sync with my android device, but it hangs on saying “syncing 99%”. And on my android it says “out of sync”. Later on I added 3 more files and now I have 4 files not syncing. As far as I remember, I did not do any changes, but somehow it does not sync anymore. Restarting both devices and syncthing did not help. Would someone please help me?

It was special characters in the filenames that prevented syncing. I have changed the names and all is fine. I do not delete the whole thing in case people would have a similar problem.