Just the main camera. The ZWO dew heater sticky-tapes onto the front of the camera body and they supplied the splitter to power the heater off of the same 12v used by the camera.
I wish I had a good physical explanation (intermittent open? cheapo thin-gauge internal wire causing a voltage drop?). I won't be 100% convinced for a while yet. With the sometimes 6-hour wait before a failure, even 20 hours of good behavior could just be luck.