DIAGNOSIS: The motor is overheating or straining immediately at startup. This is typically caused by overloading—too much thick, dry, or frozen content without enough liquid.
FIX: Review your recipe ratio. For the Ultra, you should always have at least a cup of liquid in the cup before adding solids. For thick nut butters or very frozen mixes, use the extractor blade and the 'Pulse' function in short bursts rather than a sustained run. Never run it for more than one minute continuously; give it a cool-down period.
IF THAT DIDN'T WORK: The smell could be coming from external debris. Check the bottom air vents of the base. If they're clogged with dust or kitchen grease, the motor can't cool itself. Unplug, let it cool, and vacuum the vents.
HEADS UP: A persistent burning smell, especially if accompanied by smoke, is a serious fault. Unplug it immediately and stop using it. The thermal cutoff or motor insulation could be failing, which is a fire risk.