Rekord Box Keeps Crashing on Mac

Are the other items on that playlist local (downloaded) songs, not from Apple Music?

Nope. All are in apple playlists. 

You guys need to work on library management.  Please advise

I don't use iTunes or Apple Music, because I simply never could get used to the way this program works. But that's a personal thing.

I simply convert vinyl to AIFF, or download AIFF tracks from DJ pools, and add those tracks to Platinum Notes and MiK, before I drag-and-drop them on to my external SSD drive. From my external SSD drive I drag-and-drop the AIFF files in to Rekordbox. Straight and simple.

When analyzing 1 or 10.000 tracks, never a problem with my Macbook Pro and/or Rekordbox. All runs smooth and normal. So when you experience problems in this case, I don't think you need to claim any libary management improvements, but a better work around. I don't say Rekordbox is holy software, but in your case more things could be the problem. Otherwise a lot more iTunes/Rekordbox users would complain over here.

As a consumer i have the right to claim and state my user experience. PERSONALLY.... i use iTunes and if i discover a problem i would post it to get the attention of the devs. This was never an issue in previous versions and only recently occurred. I also use platinum notes but i drag and drop into my iTunes playlists after. I also invite more iTunes/rekordbox user to state their experiences so they can see its a serious issue to address. I purchased this device and so far library management with iTunes is a becoming a pain. Another issue is cue points from serato dj. tried a few software workarounds and those don't work well. won't get into that any further but other than that this controller is awesome.