Hi Serellyn,
We believe this crash is related to one we have reported in UE-16935, but call stack is slightly different so I’ve created a second report under UE-18697 to track it once fix is implemented. We expect fix to go live in 4.9 when that is officially released, but if you’re using a source build you can grab this change:
https://github.com/EpicGames/UnrealEngine/commit/40f9df8f06384b79dc8ed9ba37ce1a2b48c90f9d
or test project in Master branch.
It appears crash is related to compiling and/or saving AnimBP and/or Character using that AnimBP, and possibly only if they reference each other in explicit casts. I’m not certain if you’ll be able to adjust these so that doesn’t happen, but it’s first place I’d look.
Hope that helps!