Instruct: Classify Amazon reviews into positive or negative sentiment
Query: poor reliability

I know many people like the product and its features -- me too, initially. But after using it for just over a year now, the slots "3" and "4" starts displaying "000" no matter what kind of batteries I put in. Sometimes, it would seems to start charging, showing the current. Then in a few seconds, it will go to "000". The manual says it will show "000" when overheat. But for me, the "000" will show up even when it first started and the unit is cold! I have the firmware 33 BTW. Slots 1 and 2 seem to be fine. Just 3 and 4. But charging 2 batteries at a time is a pain...