There are issues with the ribbon cables that connect the various PCB's together inside the console, the major problems seem to be either the aux busses, one/some/all, getting noisy, cutting out, and/or not working at all, and the same thing with the main stereo bus, the control room outs, and/or any/all of the output groups.
Mine had the problem with the main stereo bus, it would drop in volume on the left side only, after doing that for several days, it would also sometimes drop out completely on the left side only.
It spent 6 months in an authorized repair shop in the next state, and by the time I got it back I had moved "in the box" for recording/mixing, so after testing the 24x8 for about 4 hours, (it seemed to be working fine), I put it back in it's box, and it's been there ever since, about 4 years now.
Sometimes they can show almost the same symptoms, but can be easily fixed by "cleaning" the insert jacks on the malfunctioning channels by repeatedly inserting/removing a 1/4" plug in the insert jacks.