Diagnosis
No, it's not normal. This is almost always a failed control board that's not cutting power to the fan circuit after shutdown.
How to Fix It
You need to replace the control board. Unplug the grill, remove the four screws on the front panel to access the board, disconnect the wiring harnesses, and swap in the new unit.
If That Didn't Work
If a new board doesn't fix it, the issue could be a stuck relay on the newer Wi-Fi-enabled controller. A full power cycle (unplug for 30 seconds) sometimes resets it temporarily, but a permanent fix still requires a controller replacement.
Heads Up
Don't just leave it plugged in with the fan running—it will drain the battery if you're using the optional battery pack and indicates an electrical fault.