Picture freezes in the middle of playback

When a dvd or cd player freezes while playing , it could be a few differant things . First thing I would check is to make sure the disc and the lens has no dirt and dust on them, Next I would check the slider assy rail for dirt ,dust or hardened grease. Next I would check the tracking gain and tracking offsets. Without training, about the best you can do is the first or maybe the second BUT the alighnments should be left to a pro as you need alighnment disc and equipment to do this alighnment. Good Luck