I am trying the 14 days trial period and I got this problem. The UE4 Editor always crashes when I have more than one skeletal mesh using the same skeleton and at least one is not using all the bones in the existing skeleton.
This is definitely a bug in Ikinema as far as I can see.
It only crashes when I use the “Solver using Ikinema Rig” in the Animation Blueprint. The “Foot placement Behaviour” Node works fine.
I am using UE4.10.4 binary