A couple of days ago, my Nexus 7 suddenly started draining very quickly, and not fully charging overnight, even off. I have been through all the tests, cleared the cache, made sure there are no rouge programs... different chargers, cables on different wall sockets. Installed Ampere, and what I'm noting is, with the tablet sitting still, the charging amperage swings wildly, currently reporting 10 to 430 mA, but I've seen it go to negatives too. Verified on different cable/charger/wall socket. Is this normal? Anything else I can do to troubleshoot/fix?