Replicator 2X temp stops 3-5 degrees below target

I have installed multiple different versions of this firmware on my Makerbot Replicator 2x and every time, the right nozzle (T0) never reaches the desired temp, causing my prints not to start. this also happens when I try to preheat. When flashing back to the default MakerBot firmware, I have no issue. Any idea what could be causing this?