@shanttu & @m4r0v3r
I also thought "My battery is more than tight and snugly sitting.", but after inserting a piece of paper(which was quite hard, as the battery sits really tight!) I haven't had a single reboot or shutdown. That is around 2 weeks ago/
Actually prior to do that I removed the battery for 10 minutes. I also thought "What sense does it make removing it for 10 minutes and not for 30 seconds?", but I was advised by Carsten Munk(@stskeeps) of Jolla, that it is really needed. And since then - not a single issue. Of course - it can happen every moment
So even if it looks stupid - try it. And share experience here