Hi kimt1688, I still use version 2.4.1 since it works perfectly for me. I've tested every version since, but they all would fail in various ways, most recently and commonly by getting stuck saving the playlists from MusicBee to my phone. However, I can sync successfully every time in the later versions if I uncheck the "as configured in MusicBee" option.
I just decided to test a sync after changing the playlist format in MusicBee from M3U to M3U8 and WPL. Version 2.4.1 names the file "playlist.m3u8" or "playlist.wpl" as expected, but version 2.7.9 will always add a .m3u suffix to the file, so the files will be named "playlist.wpl.m3u" for example. Also, the syncing screen will show the correct name when this happens (ex. "playlist.wpl").
Please visit the following link to see what I mean:
https://imgur.com/a/Q708XLV.
I wonder if whatever is causing this behavior is what is causing the playlists transfer to get stuck indefinitely.