Fixed!
For those who are curious. It seems like TwitterKit is using core data under the covers. Well since I’m using core data and was merging contexts blindly, I was trying to merge twitter’s model into my own at some point! Doh. So the fix is to specify the context when you register for the ContextDidSave notification (as per app docs 0.o). I had specified nil which gets notified on every context change.
Shoutout to the profiler for helping debug this. I would be nothing without you!
Cheers!
Neil