Pyle PLHRDVD108KT Car Video Monitors with wireless headphones, Multicolor, 10.5 inches

At first of course everything worked, I parked my truck to go on a year deployment to Iraq when I return I was left with two screens only. Since I returned I have not been able to play single DVD on it. It takes the DVD and pushes it back out its been doing that to every single DVD. Don't but it. I have these two 10. 5 inch screen without been able to use at all.

Easy enough to set-up and use. Good picture quality. Audio will play through unit, headphones, or a selected fm radio channel. You can adjust audio preferences within the menus on the screen. Wireless headphones work well. No pairing needed. On the headphone power switch, select A or B and set the audio output on the DVD player to match (under IR setting). DVD players are in a stiff riding heavy duty truck. So far, they don't seem overly sensitive to bumps and skip or pause over rough roads. Only question mark is how to adjust the DVD players vertically. They appear to have the ability to raise or lower them on the mount, but it isn't very apparent how that feature works. There are six screws that hold the mounting plate to the rear of the unit, but two screws are behind another bracket. Without removing all six screws to loosen or remove the mounting plate, the ability to adjust the mounting height vertically seem limited. Any insight on how to adjust the height (up or down) on the back of the unit so it sits higher or lower on the headrest would be welcome.