A few days ago my Tesco Hudl 2 battery decided to expand it's waistline and pushed the LCD screen outside the confines of the case. I've now taken it to bits and am awaiting an eBay 'new-old stock' battery to fit in replacement.
In my view these things may go a bit mental if
1) kept on charge 24/7 and little used 2) it's hot 3) someone (kids) start mishandling such a damaged item.
Same thing happened recently to an old Sony Erricsson phone, I placed it on charge and then found I couldn't slide the battery out.