I found a bug 
:
If you rapidly change the transparency of a part welded to your skinned mesh or the skinned mesh itself, the mesh reverts to its non-animated state for one or two frames then changes back.
Video:
Place:
SkinnedMeshGlitch.rbxl (31.5 KB)
I ran into this problem with a custom skinned mesh I created and it looked pretty bad with the mesh glitching.
Edit: changed video so it isn’t laggy