I have the VT75 Nano and i have the same problem that Jez650 and other people have. The precision of the TC is frustrated by the issues caused by the cover of the battery and the 510 plate. It is necessary, in my opinion, to clean frequently these items. Only one clean doesn't fix the problem forever! Poor, in my opinion, mechanical project (threads between two different materials is not good) that brings to electrical malfunction. I apologize for my english.