Replaced the disk laser on PS2 SLIM; drive motor now slips

Hi,

I just replaced the laser on my ps2 slim. I was testing it, put in a cd game and pressed down the two sensors for the door. The game starts to spin, then suddenly stops when the drive shaft send the laser down. It gets stuck there now until it stops. When I move the laser manually,it seems fine. I tightened the screw, but not tight enough to strip or break anything. I’m at a loss, not sure how to fix the problem now.