So you still can try to update? Have you tried legacy mode? It takes ~10 minutes to update that way, but might help. Different phone/tablet might also do the trick.
Almost empty batteries might also do strange things..
Killing (or even removing and reinstalling) the app and bluetooth on your tablet might also help.
Then just repeat those steps in random order for couple hours and hope for the best :D .. When everything fails, ask for a replacement..