I've tested the unit in several PCs, and it has the same problem.
I am under warranty. I took the unit to the shop and they pick it up to get a new one. Meanwhile they gave me two broken drives to test (GSA-4082B and GSA-4120B). One of them had the same disc motor problem, and the other needed regreasing, but only reads some CDs. If I manage to repair the last, I will have two by the price of one