SACD Player Won't Play Hybrid SACDs

Thanks for the info, Chayro. I wish I knew what it all meant. However, I'm certain the problem is not an alinement or cleaning issue. Over the past few days I have done some "testing." When the player has been turned off and sits over night or is turned off for a while, cools down and turned back on, it plays fine for a while. It correctly reads any combination of SACD and CD disks that are loaded into the changer. However, once the unit is on for period of time (give or take 2 hours), it stops reading SACD and will only read the CD layer. It won't stop reading SACD midstream during a disk play. Once it recognizes SACD, it will play the disk to completion and then stop SACD recognition on subsequent disks.
A few yrs ago, the unit was modified by Matt Anker of SACD Mods. He said the unit would run warm and it was normal. The unit played fine until recently so, I don't think the problem is related to his mod (which had nothing to do with the actual disk layer reading). I tried to locate Matt just to run the issue by him, but he is no where to be found.

On my sony 5400, you can only play sacd in sacd mode with the internal dac. The digital output only works with redbook.

Sounds like weakening laser/read - lifetime is about 2-3years. Change the optical
assembly and you should be fine. Can be had from e-Bay for around $30-60 depending
on models.

My old dCS was fitted with Sony's SCD555ES equivalent, and I had to change them out
(optic assy.) once every 2-3years. Basically similar problems you encountered.

I dropped the SCD-C555ES off at the local Sony authorized repair shop. The place has an excellent reputation and does service work for just about all brands. The problem is the optical assembly. They're waiting for the Sony part to come in. Should be good to go.