DIAGNOSIS No, it's not. The fan should shut off after the cool-down cycle (about 15-20 minutes). Continuous running indicates a controller software glitch or a stuck relay.
FIX Perform a hard reset. Unplug the grill from the power outlet. Wait for two full minutes. While unplugged, press and hold the power button on the controller for 10 seconds. Plug it back in and restart.
IF THAT DIDN'T WORK The issue may be firmware-related. Ensure your grill's firmware is updated via the Traeger app. If the problem persists after an update, a controller replacement is likely needed.
HEADS UP A fan running indefinitely will drain the battery backup on the controller, which can cause Wi-Fi pairing issues and 'err' codes on your next startup when AC power is restored.