DIAGNOSIS: The motor is overheating, often because you're overloading the jar or running it too long without a break, causing the internal components to overheat.
FIX: Immediately unplug the blender and let it cool for at least 30 minutes. For future use, never fill the jar past the 40-oz max line. For thick blends like nut butters, use the pulse function in 10-15 second bursts with 30-second rests in between to let the motor cool.
IF THAT DIDN'T WORK: The burning smell could be from food jammed against the bottom of the jar, overheating the blade assembly. Always ensure there's enough liquid to keep ingredients moving, and use the tamper through the lid feed chute (if your model has one) to push food down, never a utensil while running.
HEADS UP: A continuous burning smell, even with proper use, indicates a failing motor or wiring. Stop using it immediately—it's a fire hazard. The motor base needs replacement.