Is the bowl too tight?
Unlike the glass bowls, there is NO removable thread ring on the ceramic bowl—the ceramic bowl threads directly into the base plate. Depending upon how tight a fit, you may see marks or discoloration when removing the bowl, called "nickeling."
The same nickeling will be found on the inside of the bowl if the beater is too low and hits bottom. It is essential to make sure the beater to bowl clearance is correct and to clean the bowl.
These marks can be removed with an abrasive cleaner.