Since this issue seems to still be an issue at least with 5.2, figured I’d give this my solution in case anyone else also runs into it.
While disabling and enabling the collision works, that may also break other responses momentarily, so I found this neat little method buried in there.
Edit: For a BP you’ll need to use a BlueprintFunctionLibrary per my other response here, but it still requires a C++ project. I don’t really have a solution if your project is BP only.
InstancedStaticMeshComponent* MeshInst;
// ...
for (FBodyInstance* body : MeshInst->InstanceBodies)
{
body->CopyRuntimeBodyInstancePropertiesFrom(&MeshInst->BodyInstance);
}