Generally speaking, Promags suck. I don't think I've ever had one function 99% in a gun regardless of what gun/mag I've tried them in.
If you think it's the follower, you can try swapping them. In my opinion you'd be better off just ditching the Promag.If you really want a 10rd mag for the 220, get one from Sig.
As for the other problem, I never had that issue with my 220. Sorry.