It is my opinion that the machine is not balancd or possibly the delivery co. some gorilla on the way mishandled it. we all know that bowling balls are not perfectly balanced right? Also the machines that the pro shops use are industrial quality and in many cases bolted down, I'd be afraid very afraid to bolt an at home/portable product down. It all comes down to BUYER BEWARE,YOU GET WHAT YOU PLAY & PAY FOR. For my money I'll trust my local Pro to adjust my cover stocks, he never charges me for this anyway. HE WHO DIES WITH THE MOST TOYS WINS