DIAGNOSIS: This is a known failure of the mechanical timer mechanism. The internal gears or spring are defective. The dial feels loose or spins too freely.
FIX: There is no user fix. The timer is integrated into the main control panel. The entire unit must be replaced under warranty. Contact Chefman support. Have your model number (usually on bottom label) and purchase receipt ready.
IF THAT DIDN'T WORK: While waiting for replacement, you can manually monitor cook time with an external timer. Unplug the air fryer to stop it, as the timer control will be unreliable.
HEADS UP: Do not attempt to open the control housing. It contains live mains voltage even when unplugged due to capacitor storage. This is a serious electrocution risk.