Looking for explanations to ML390S ERROR= codes please

Have you contacted the manufacturer?   That is my first suggestion.  I had a number of errors on various CD players in the past and they all cleared up when one of the following happened;  I cleaned the CD, I cleaned the CD lens using an appropriate method stated in the manual, or lastly, I replaced the CD with an identical one that didn't create errors.  If you still have errors after that, the CD unit needs a service call of some kind.   

Well, the unit's laser lense was replaced only a few months ago and it worked just fine until just now. 
The technician says "only the designer of the software would know" (if after 25 years he'd be still around...?!?) 
Contacting Harman seems questionable at best, also since I'm residing in RSA. 

The distributor wants to sell new stuff, and points me to his now freelance technician - who doesn't know, as already mentioned. 
Maybe I'll play the 'offending' CDs on my dirt cheap LG Blue Ray Player by using Toslink going into my ML36 DAC.?!? 🥴 
I keep my CDs *very* clean, and also it seems to have something to do with the 'quality' of SACD/CD discs... 
M. 🇿🇦 

Yes, check the CDs on another player. CDs sometimes get "disc rot" with age -- they look fine but won't play, skip or have distortion. It usually ties back to oxidation due to manufacturing problems. This is fairly rare, though.

For the player itself, it sounds like perhaps the lens has either gotten dirty or is out of alignment. Like any mechanical device, things do wear with age, or perhaps the settings weren't tightened properly when your unit was recently serviced and the lens is out of alignment. There is a lesser likelihood that the new laser unit has gone defective. In any event, if it is not the CDs themselves, it is time to go back to the shop for another round of service.

Thanks for the kind responses,
one more curious thing to mention is, when opening the load-tray and rotating the CD by a few degrees it sometimes plays just OK right through.
Additionally by trying a few restarts, can also do the trick... 
 
However,
I feel that knowing what exactly those two error codes (7 and 10) try to communicate, might help explain what actually is the case when the disc is being refused, by the message displayed: 'NO DISC' ? 
M. 🇿🇦