Hi. My makes that noise too but not reading disc. Laser is moving but the disc spins only a little and that is all. But when I close empty tray, it spins normally and says no disc :/I found that this sound is normal, i don't have the problem with the bad reading or mixed disc, it do a weird sound/movement before it begin to read a disc and is because its checking the limit of the rail, its exactly like phat liteon work. The original pcb board don't do that noise. The LTU2 PCB work perfect with that weird sound(i tested 9 boards, its the same with all of then).
You can clearly hear it when you power up the Console.