Optical Drive not working.

Heyy,

I had a PS2 Slim (Pink Version) SCPH-77004 with a broken shell (the rest was completely fine)

To replace the shell I ordered a defective and labeled as "Don't Reads Discs)"(Same Type, Same model of course) (might be a different MB Version, didn't checked)

The spare wasn't opened before. Like described it booted and was behaving normal in home screen, it didn't read a disc, but furthermore it didn't seem to even show life of the Laser Assembly (no Motor Spinning, no Laser movement)

That's when I started disassembly, first I checked/tested the two lid switches, both pressed, same result. Both tested good with a multimeter

I tried the working Assembly from my own Slim, and had the same result. The rail tested in my Slim showed Laser Movement and the motor was spinning up. (Didn't read discs, made clicking noises)

I did the same thing with the ribbon cable (so using the ribbon vice versa on both machines) which also provided the same results, I inspected the board of the Spare one and didn't saw any (obvious) issues. And I also checked the Ribbon connectors for lose (cold) connections.

The Spare also didn't looked dirty inside at all, it was like opening a never used console.

So in short:

Laser Assembly good

Ribbon cable good

Ribbon cable connectors good

No obvious MB issue (with Eyes)

Lid switches fine

My question now is, what could it be? Where could/should I start looking for an issue? Did anyone had a similar problem?