How do I get my lab to stop shaking her head while she is comming back with the bumper or bird. She doesnt shake it like a bulldog its more like she is playing , but she sometimes drops the bumper. She also wants to cigar the bumper alot. 3 inch bumpers are the biggest problem, its like she dosent want to open her mouth wide enough to get a firm grip. She is force broke, but maybe I should put her back on the table?