Forerunner 245 music database corruption - even with 3.77, clean Windows 10 and new Garmin Express.

Still struggling to understand what goes on when I transfer a large list of songs and the watch gets befuddled.

The watch has 3.77 firmware, and I did a clean install of just Windows 10 and Garmin Express to a virgin machine.

I take a big list of songs in My Music, and transfer.

(1) About 600MB of songs make it across, some songs "are not transferred", then it says transfer complete.

... At this point the watch sees and can play the songs.

(2) Reconnect the watch and re-start, another 600MB makes it before failure, then it says transfer complete.

... At this point the watch *cannot see or play *any* songs*.

... But Garmin Express shows "My Music 1.3 GB and Free 2.3 GB".

... Even though Garmin Express shows *no songs* on the watch.

Something fishy is going on here?  At this point, my strategy is to stick to just small playlists, because large music sets fail in weird ways?

I'm guessing that the stated "500 song" maximum even though the watch has 3.7 GB storage is because the watch's database can't keep up?