I used a new 3rd Person project in 4.13.2 for these tests. This is a serious bug that causes the Skeletal Mesh to “explode” and self-destruct, which sometimes results in UE4’s shutting down. The bug is caused by making multiple calls to “Set All Bodies Simulate Physics” or “Set Simulate Physics” (or any node that turns Physics ON) on a Skeletal Mesh that has a Scale less than 1,1,1. Through multiple tests, I determined that this occurs when the Skeletal Mesh’s final World 3D Scale becomes less than 1,1,1. For example, if a Character is used and the Capsule Component (root) Scale is increased to 3,3,3 and then the Skeletal Mesh is reduced to 0.5,0.5,0.5 (making its final Scale = 1.5,1.5,1.5), there is no problem. Similarly, even if the Skeletal Mesh remains at 1,1,1, setting the Capsule Component (root) to less than 1,1,1 will also cause this problem.
I found that turning the Simulate Physics to OFF using a Flip Flop will prevent this problem (unless the calls are made too rapidly, like when using a Tick / Timeline). However, I know that for many people (myself included), it is not feasible to turn physics off and then back on just to avoid this error.
Please let me know if this is unclear or you would like me to do further testing. As a workaround, I was considering re-importing all of my Skeletal Meshes so that, even when I shrink them, they will never reach less than a final World 3D Scale of 1,1,1. Unfortunately, importing Skeletal Meshes that are too small can also be very difficult and has its own set of problems…