Diagnosis
The motor is overheating. This is almost always caused by overloading the jar or using it for too long on high speed.
How to Fix It
Unplug it immediately. Let it cool for at least an hour. For future use, do not run it on the highest speed (the 'High' or 'Crush Ice' setting) for more than 60 seconds continuously. For thick mixtures like nut butters, use pulse.
If That Didn't Work
The thermal overload protector inside the motor housing may be failing. This requires disassembling the base. Not a user-serviceable part. Contact Hamilton Beach.
Heads Up
That smell is the insulation on the motor windings. Repeated overheating will kill the motor permanently.