What is This Noise?

I recall encountering this same effect many years ago. It did sound a lot like static. The weird part was that it only seemed to happen on a very few particular spots on an equally few CD's, yet there would always be no visible defect on them whatsoever. What's more is that the noise was entirely repeatable, backing up and replaying the spot invariably gave the same results...and the specific *character* of the sound of the noise would not change one iota when you did replay it - almost like it *was* disc defect - except it wasn't. The disc would look perfectly clean and no amount of wiping them down seemed to change anything. CD pressing defects?? Fast forward a decade or so, after many iterations of system changes (better wiring, some power conditioning, component changes and various tweaks) I one day realized that I was no longer hearing this noise at all, but that it had seemed to fade away by degrees. By that I mean that, at first, the noise just seemed not quite as 'loud' as before, then at some point later in the system evolution it was like some of the affected CD's were no longer exhibiting the problem while others still were. Finally, every problem disc that I had, had eventually been 'freed' from that effect and it has remained so ever since. For the past 7 or 8 years or so, not only has it not recurred, but I would somehow be shocked at this point if it did. The system these days is operating at a high level and all my usual-suspect (soundstaging, dynamics, etc) vagaries have been successfully worked out and, as a byproduct, all things electrical concerning the system seemed a bit more 'stable' (the sound being less affected by things like "popping" when turning on or off a particular light switch, time-of-day voltage sags, etc). Again, no sign of the noise anymore, these days. But, I never did come to any real understanding of what phenomenon might be involved or what might have caused it. My best guess is that it may indeed be related to static charge, but that my 'problem' CD's (which are now for me problem CD's no longer) may have managed to 'trick' or 'induce' the player to audibly stumble in that way - something in the musical signal at some particular spot on the spinning disc may have been enough to trigger interference with some 'borderline' condition existing either in the system as a whole or perhaps the CDP itself...the combination of static and digital "self-noise" anyone?? I don't really know, myself. Have never seen the phenomenon referenced anywhere outside this thread that I recall...