well, here is the latest.
After having lost the power over part of the house (and recovering it by turning the oven on) several times, I got the utility to come by and check their side of the system. They did, and said after a load test that their side was good.
He looked at the breakers with a FLIR camera and commented that the main breaker might be slightly hot. 74F vs 71F for the ambiance so not really much. Maybe just the normal current going through? We may have also heard a click come from the main breaker but not obvious at the time, could have been from the meter clip, cuz
he then pulled the meter out, at the same time pulling one of the meter mount clips off the bus bar with it.

Apparently, the clip was loose or broken off. Which means one of the panel bus bar was perhaps earlier disconnecting or erratic connection (and maybe causing the partial blackouts for circuits on that bar?) as it looked like some arcing took place between the clip and the bus bar. At that point I was up the creek with no more power to the house. Great... Bad surprise.
Friday evening, no power. Getting an electrician to come would have been both expensive and likely fruitless as he would have no doubt declared the whole box toast and declared we need to replace all the inside since it's 22 years old with likely obsolete hardware, which would have been a big job. (Flushed box installed in the outside stucco wall no less, so can't easily replace the whole thing.)
So I rebuilt the meter mount myself. All bolts corroded so that was no piece of cake. Had to remove if from the bus bars and all to get to the clip mount bolt. $3 in new bolts, 5 hours or so. That included rethreading all the holes, putting antiseize on all new bolts etc. A beauty.
Got the utility to come back to reenergize it all.
Power back. But the main breaker still appears to be clicking every so often. Maybe that is causing the slight undervoltages I'm seeing at my computer.
So far, we have not lost all power to half the house again. That may have been caused by the loose meter connection, likely. One 120V line out and some of the circuits off the subpanel off too then. I'm hypothesizing that maybe turning the oven on upped the load enough to cause the meter clip to arcweld itself back together. No idea if that's even possible.
So now, I've got power again but may have a main breaker on the fritz. Old so maybe no easy replacement. Plus it does not look easy to take out, even without the corroded bolts I have. Sheesh.... I hope I don't have to replace all the insides with it. I wonder if the main breaker could have gone bad because of the bad meter connection.
At least it's safe, no fire risk, according to the crusty old electrical contractor boss that came with his utility staff guy to check things out. But the main breaker could well shut itself off permanently if bad, he said.
And now, I know how this thing works, 240V and all, so that's good.
When was the last time you had to take your main panel apart...?