why do cd players "sometimes" not read a disc?

My Lexicon RT-20 is sometimes refusing to read a disc that has just been playing?
perhaps laser pick up is dusty or dirty(prefer opening and cleaning explicively vs. using clean disk that never works), or as gears moving it gets misaligned within time. paid lotsa money, than gotta ship it tofrom repair facility...

that's why i love my analogue!
Often it is because the laser has become dusty/dirty and a simple cleaning will take care of the problem.
this was episodically a problem with my Linn Genki in longer playing sessions. The end culprit was wear on the transport surface that gripped the top of the CD... the CD slipped when the player was warm. The fix was to build up the grip surface with thin frictionable tape which required opening up the player and the drive. A more cumbersome approach is the stick on CD rings but that's probably a good diagnostic approach if a CD has intermittent problems. If you try the stick on ring and the problems disappear the answer is found before taking the risk of working on the player.
why do cd players "sometimes" not read a disc?
Transport broken?

that's why i love my analogue!
That's why I love my music server.
The RT 20 is a killer player. I would consider a 'tune up' if it is older than 5 years.
Kng, I love my music server too!
Czarivey, one of my USB external drive died but luckily it was backed up. It cost $89 so no big deal but if a CD player drive dies, a different story. Back up your music!
Thanks Jafant. I have been pleased with its sound; but I found it benefited "dramatically" with ac isolation and conditioning.
I found conditioning and isolating the ac provided a quite remarkable transformation.
It makes me very curious about what internal parts related to power supply should be upgraded, and how.
I find moving the disc around in the tray can result
in it playing. What gives????? Can it be dirt on the laser?