Guys I sell playstations, ALLLLL the time - that means I test them constantly and thoroughly. My burner is external USB, and my last was internal SATA - both had minimum burning speeds of 16- no issues in ANY of the (at least 40 by now) playstations I've run the discs through, other than the ones with dodgy disc drives. You can try turning the dial up a TINY NIP on the side of the laser, it won't hurt. I usually turn it a wee bit on every console I've modded. The burnt discs don't have as much reflection as the originals.
Other than that, the lasers are usually shot / on their way out.
Also note
Unirom isn't the only package with freepsxboot.
I just finished informing the Tonyhax author about his misguided info on the orca site - he has the builds with freepsxboot in his packaged downloads with each version since freepsxboot was released, but for some reason, he guides people across to the Github for freepsxboot which contains only builds with Unirom.
I'd suggest only using Verbatim AZO if you can't get your hands on Taiyo Yudens (That's! CD-R)
Also check out my new modchips:
Here's a demo of the one for PAL PM41
https://www.youtube.com/watch?v=Ahy8XMkAvQc