So as i understand the old batery over heated and warped the device which still works fine however you put a new batery in an its not operating as it should. In this the new batery will never work corectly(lucky it even works in the device) as it wont fit into the warp shape and im surprised the batery contacts sit right. The fact the batery works is good an not the trubble however the device. The device was made flat an now its dished which meens your screen is going to act up add in a heat damaged board. I can only say replace the board an screen or send it to your bone yard and get a new one.