Unreal Engine 4.16 seems to have introduced some odd physics instabilities. Create a new first person shooter project (blueprints or C++) and shoot the top of one of the boxes. It doesn’t come to a rest properly but instead dances around randomly. I tried messing with the physics settings to get rid of this but didn’t have any luck. I even enabled physics sub-stepping to no avail.
I took a video as proof I’m not going crazy: UE416 bad physics - YouTube
I checked and this behavior isn’t present in 4.15.3.