Sometimes, when I try to edit a bone in an animation sequence, then add a key and apply it, UE4 crashes with this error. What’s weird is that it’s only with specific bones. So on some animations, it crashes every single time I try to edit a part of the thumb or index finger bones, even though I can edit them fine on a different animation sequence. The finger bones are the most common parts that cause UE to crash though. I couldn’t find any forums discussing a problem with keys being the cause of crashes.