RS1 "upgrade" definitely added instability to my SP4. It failed the first time, refusing to go past the Surface logo. It required a system restore just to boot; and then reapplied the updates. It booted up this time, but well, it was downhill from there. Starting having issues with heating up, Edge using up way too many resources, action tray wouldn't always respond, battery life went to crap, etc.
None of my other devices have experienced issues with RS1. So I just did a full "remove everything" factory reset. Now it's running great (again).
Microsoft took a good 6 months to get to what I felt was a "stable" working state with the SP4. It's unfortunate the big update isn't going that well for some of us. Admittedly, I've installed/uninstalled plenty of stuff over the past few months on the Surface. So who knows what single or combination of events are at fault.
Fortunately, factory reset got it back to a happy stable place.