Sync from TuneFUSION on Windows to FooBar2000 Android seems to be stuck:

Sync started on Friday, April 5, 2019, 17:17:34 PM to foobar2000 on Google Pixel 3
Library contains 13177 tracks, 12580 tracks requiring syncing
Sync incomplete.

It has been at "12580 tracks requiring syncing" for many hours now.

Windows log show some files with the error:
Storing Zbs Foundation/Invasion.mp3
Unable to store Zbs Foundation/Invasion.mp3

Some filenames have special characters, but not all of them do.

...with no other error shown. There is 78GB free in the destination, so I cannot tell why it would have a problem storing some files.
Sync started on Friday, April 5, 2019, 17:17:34 PM to foobar2000 on Google Pixel 3
Library contains 13177 tracks, 12580 tracks requiring syncing
Device has 78 GB free space, 466.31 MB already synchronized

On the Android device, the FooBar2000 app under "Sync with TuneFUSION" sometimes says "network timeout." With no other error, network is otherwise fine, it seems like it is just waiting on TuneFUSION.

Please advise, cannot tell what the actual error is as there are no other error messages that I can see.