Taz6 fails heating at 184 degrees

Taz6 will only heat up to 183/185. then gives heating failed message. this is a loaned machine in a makerspace so I want to mess with it as little as possible. Heater or thermistor? The temp stays constant at 184. Aerostruder hotend.

Does the value change, or is it stuck?

If it is stuck, I would think thermistor or bad wire or maybe wrong firmware?

If the value changes, on a different printer I was having similar issue where it was not reaching heat setting. I turned down the cooling fan on startup and then re-enable fans when running. Then it appeared to keep up.

Updating the firmware seems to have done the trick sort of. Reaches 220 now no issues. 3 or 4 layers into print it fails “thermal runaway”. Last time that happened, the silicone sock was missing, and a new one sorted that. Not the case this time.