This is obviously not the motor since turning the smoke unit off solves the problem.
What has likely happened is the smoke triac has shorted on the R2LC and it's providing the smoke unit with full track voltage instead of half-wave track voltage. That being the case, instead of around 6 watts in the smoke unit, it's getting twice that much power and overheating. Spectacular smoke, but it cooks the smoke unit in the process if it goes on too long.
The fix will involve getting the smoke triac on the R2LC replaced (if it's damaged the PCB, you may need a new R2LC). Next, you'll need a smoke unit build at a minimum, and likely a replacement PCB, see below. At a minimum, I'd replace the smoke unit resistor and the wick material in the smoke unit.
