Could be a lubrication issue. You might try removing the cover and see if you can lubricate the rails on which the laser assembly moves back and forth. Use a plastic-safe grease.

Another possibility is the laser is going bad. I've had that happen on some older units. The part is generally about $75 but the catch is you generally need test equipment to adjust the assembly after installation, and would also need the service manual to see what the exact procedure is. This is not a DIY project for most people.