Is the head of the mixer locked into place?
If the beater is too high, the mixer head cannot be locked into place.
CLICK HERE for more information on how to lower the beater.
Is the beater scraping the bottom of the bowl?
If the beater is too low, it will push into the bowl, and cause the mixer head to bounce.
CLICK HERE for more information on how to raise the beater.
Is the silver pin on the base of the mixer loose or protruding?
If the silver neck pin is loose, it can cause the mixer head to bounce.