Hi!
You are right. Replacing the drive will probably not fix this. Replacing the laser deck usually always work. When it's trying to read the disc, do you hear the laser actually trying to read it? If yes, then it's pretty sure that the laser is having issues.
Maybe you bought a faulty laser deck. I would return it and get yourself a refund and buy it somewhere else (or return it and get yourself a new one).
It's most likely the laser deck again.
If you have any questions, please let us know!