Another issue with NPCs, although not crashworthy:
Telling a follower NPC that you’re going to go on your own sometimes bugs out the NPC, leaving them unable to rejoin you, effectively making them back into a wandering NPC.
I’ve tried it on eight of my follower NPCs on the same save, and it seems like it’s completely broken. This worked fine before, so I’m unsure whether or not it’s a consequence of having many NPC followers, or some internal save variables flubbing up.