It could be in the power supply board -- op or caps. I'm guessing from a similar problem I had years ago: the technician changed the op amps.
Ken it sounds like you're onto something with the freezer trick. Have you heard of freeze spray? Get a can of that & when it starts skipping, cool the individual onboard component parts each with a small blast to see if you can isolate the problem part.
Electrolytic caps do dry out & degrade, so it might pay to replace them; start with the readily available ones first of course.
I had two micromegas, Stage 3 and Stage 4. Both had the skipping problem which seem to plague the Stage line. Worst part is that I could find no audio repair that would touch either one. To make matters worse Micromega is not distributed in the USA any longer. A company could Dimex located in Canada use to service Micromega if you sent it to them. They won't do it any longer and I was told by them that the problem is with one of the proprietary modules in the unit.....essentially it cannot be fixed unless you can send the unit to France or get the parts outside the USA. I just chucked both of mine because the problem became to annoying and I got no response from Micromega when I tried to reach them. Nice sounding units but Micromega can stick it up their you no what.