I was having a lot of problems with various blu ray discs not playing. I tried resetting the player, turning off internet access, etc. Sometimes these procedures would make the disc playable. But more and more often nothing I did helped. I checked with Sony. They would try to repair the player for ~$110 or swap it out for a refurbished player for ~$230. To me, neither of these options is cost effective. I would sooner buy a new unit.
I decided to disassemble the player and clean the optical lenses. This turned out to be not too difficult. The hardest part was removing the cover. After spending about an hour trying to remove the cover I decided to download the service manual for $10.
To get at the lenses, I had to disassemble most of the player and remove the disc drive. The disk drive is self-contained, similar to what is in a desktop computer.
I opened the disc drive and wiped the lenses with a q-tip dipped in alcohol. There are definitely 2 lenses (a blue and a red one.). Reassembly went pretty quickly after the experience of taking it apart.
So far it worked!!!
A disc that I could not play previously started right up.
I have to say, I don't recommend this for the weak of heart. Although there was nothing "tricky" (except for the cover), I did have to remove several PC boards and disconnect many connectors, including ribbon connectors. But it is definitely doable.