there isnt a whole lot to temp control contrary to the stories of magic that evolv has sold everyone -- hysteresis is the hardest thing to nail down perfectly and i would bet thats the issue you are having -- there is likely an interupt being called before a timer runs out and that causes it to freeze up because that wasn't properly planned for.
see if you can get it to more consistently have the issue when its cold or hot out -- see if you continue to inhale after letting go of the fire or start inhaling earlier than normal if that contributes to the issue. once you can give them a path to consistently reproduce the issue they will do it on their side on a unit that has a debugger attached and be able to see exactly whats causing the failure -- hopefully they were smart enough to include a way for you to upgrade the firmware to test the fix like via usb upload like
ipv did. Good luck.