How to stop this piece from shrinking or flattening?

Hi, so I have been trying absolutely everything to try and get this shoulder piece to stop flattening in studio when being worn.
I have done the following: I have adjusted the outer cage to go over the shoulder piece, and I have left the caging off the shoulder piece (which is what you’re supposed to do when parts of your clothing have extrusions)
I have made sure that the piece has proper weight painting, then I removed any influence at all.

I have tested every one of these and nothing helps at all.


is what it should look like

and how it keeps presenting itself.