Printer stops while printing because 'Heating failed', connection closes about marlin-ai3m HOT 3 CLOSED

Actually, after researching a bit more I think this is probably not related to the FW. Feel free to close the issue if that's the case.

from marlin-ai3m.

That's just a native Marlin feature - If your heater fails to reach or hold a certain temperature over a certain amount of time, it will cancel the print as a security measure.

Not really related to my particular firmware, though we can still try to work this out. Did you do a PID tune? Those might sometimes result in less stable temperatures or even failing to reach desired temperatures. Try using the default values from the readme.
Did you limit your parts cooling fan? As you know, this Firmware unlocks the full 12V, which might be too much cooling on the stock parts cooler. You should set it to 60-70%.

from marlin-ai3m.

Thanks, I re-adjusted the cooling fan speed to 70% as suggested, and restored the default values for the PID. I hope that fixes it, thanks for your help!

from marlin-ai3m.