Does the beater need to be adjusted?
If your flat beater is hitting the bottom of the bowl, it's possible that your beater is too low and needs to be raised. Your mixer is adjusted for optimum mixing at the factory, but through time and use it can change, and it should be readjusted.
If the beater is too low and pushes into the bowl, it can cause the bowl to become scratched, and the head of the mixer may bounce up and down.
If your flat beater is white, it's possible that the white coating may chip or become worn on the bottom from hitting the bowl, and should be replaced.
CLICK HERE for information and a video on how to adjust the beater to bowl clearance.