Disc spins for quarter of a second, then suddenly stops

So, I've recently opened a PS2 Fat handed to me by a friend of mine to fix some issue with the reader.

Video okay, inputs for controller ok, fan ok and else, with the only issue being in fact, the reader.

As taking a look with the optical reader opened, I can tell that the disk spins for a bit, and then suddenly stops.

I can't really tell if the problem is the spinner, a dead laser or a faulty laser cable, since I can't really check the laser light.

Does anyone know how I can track the issue?