Power Assist Brake problems of the 2012 GMC Sierra

2012 GMC denali. Consumer writes in regards to vehicle steering problems. The consumer noticed a very bad problem with the steering whenever he slowed down to turn, he would loose control over the ability to turn. The wheel locked down when he applied the brake and tried to turn at the same time. He was not able to turn until he pressed on the accelerator or released the brake. The dealer said it was caused by the power booster taking all the power to the brakes and leaving very little to the steering. Also, there was a problem with the back-up screen. The picture was extremely dark, and it was hard to make out the images on the screen. The dealer tried to lighten the screen, but to no avail.