I've been making good progress dialing in the print quality for the past week before this. The temperature just dropped suddenly. Mattercontrol stopped the extruder motor for safety. The printer just continued printing in mid-air before I stopped it. The temperature probe reads properly (24-25C). I touched the hot-end to verify that it's cool. The red heater LED on the end-effector PCD lights up. I disconnected the heater cable and measured 24V across the pins. I checked that the heater cable is not broken. Isn't the heater element just resistive? I can't figure out what could be broken. Any suggestions on what I should try next?