Talk to some of the guys at your club that have some experience with this gun / and with taking a stock off this gun - get their input first.
But I would take the stock off first - or talk to your local dealer where you bought it and see if they want to do it ( but I know I'm careful / and I've taken stocks off of XS Skeet models dozens of times ...) and some dealers aren't that careful ... ( make sure they lay it down on a towel, etc ) so it doesn't get all scratched up...
Since its under warranty / if you can - you need to figure out what is loose or broken and rattling - before you send it to Browning because honestly, it might be 8 or 10 weeks before you get it back .... If its a major item that is broken, I would send it back to Browning or at least talk to them ...find out if you can have a local gunsmith do the work ...
I don't want you to give up on this gun / I have 5 of the XS Skeet models ( 12's, 20, 28ga and a .410 ) - and I've never had a spring or anything else break / in many thousands of shells thru my guns .... ( and I have several other models of Browning O/U's - XT's, Lightning, etc - and none of those guns / new and used have ever had a broken part on them ).... In my experience what you're experiencing is unusual - but you still need to fgure out what the issue is ??
I see dozens of the XS Skeet models at Skeet and Sporting Clays shoots in my area - and I can't say I've ever heard of any issues with this gun / other than wearing out firing pins ..... so I'm just saying, don't sour on this gun .... hopefully, whatever it is, is a quick and easy fix...