Charger Problem

Im having this weird issue with my Bantam BC6-10 when charging lipos in balance mode (which I do every time) it seems that recently over the last couple of weeks my charger never seems to finish a balance cylce. It will charge/balance the batteries normally and drop charge amps as it goes but once the battery gets to 8.40 volts and the cells to approx 4.2 volts each it basically keeps on going trying to balance at like .1-.5 amps or so for hours at a time it never seems to finish. I have tried this will 3 different 2s (2 orions and a thunder power) batteries and a 3s (zippy) and same result it never finishes the charge cycle, which it alway used to do. Any ideas on what might cause this, I couldnt see any setting that I might have messed up on it.