[spooky]

I dont think that your laser is screwed at all!

I have only come across this once before and that was with an old SCHP-100x (the original PSX, not PS2) and i found that laser tweaking solved some of the porblem, but not all!

In my honest opinion it sounds like resonance of some sort, possibly caused by a dodgy moulded case which becomes more apparent after it has been pulled apart and modified. (this is a complete and wild guess!)

It may be worth while making sure that everything is seated correctly and ALL the screws are done up tight! (sounds daft, but then again so is resonance!).