"Too many files open" error when syncing an iPhone

For the last month or so, every time I try to sync my iPhone XR to iTunes (on a Mac) I get an error:

This started happening when I tried turning on Wi-Fi sync between my phone and my Mac. I have since turned it off, but the error persists. I have rebooted my Mac and my iPhone multiple times since then to no avail.

Other devices (an iPod Touch, two different iPads) synchronize just fine to the same computer, and my photos are able to transfer from this iPhone to Photos as well.

Any idea what's going on and how I can fix it?

There are several threads about this on the Apple discussion forum, but all of them have gone unanswered for many years.

Solution 1:

This appears to be a bug with current versions of iTunes, and may be fixed in the future.

In the meantime, a workaround which sometimes works:

1. Disable "automatically sync this phone when connected"
2. Turn off music synchronization, and click "remove" when it asks you if you really want to stop synchronizing to this library
3. Sync the phone manually
4. Turn music synchronization back on, and then click "remove and sync" when it asks you what to do.
5. Sync the phone manually

After this point the library seems to be repaired and it starts to sync again, at least for a little while.

UPDATE: This technique stopped working for me (or rather, it failed to work; thanks, confirmation bias). However, doing a backup of my phone, and then restoring it from that backup, usually works. Eventually.