Hopefully final update:
I got 4 new batteries yesterday. Installed this morning. I wasn't clear on this earlier but they're Group GC2 6-Volt, and NOT Group 24 like I thought. Which makes more sense, because I couldn't find any flooded (not sealed) 12v batteries.
The old batteries are all reading right around ~5.96-6.06v.
With new batteries in, the Magnum's not flashed a fault or acted up at all. Also, I emailed Magnum and they got back to me pretty quickly saying that bad batteries will make the Magnum act up in strange ways:
> Yes, if the batteries aren’t able to hold a charge and we are trying to load them down, you could see all sorts of odd things. If the batteries are really old and just won’t maintain a charge no matter what, it’s best to get new batteries.
The strange thing that I still haven't figured out is why a few of my outlets were losing power. The outlets in question are the furthest back in my coach, closest to the inverter. I'm wondering if perhaps those outlets might be wired differently from the rest. (Like maybe they're dependent on the inverter, even when plugged into shore power. Not sure that makes sense.) Either that or the power from the RV park was acting up at the same time, and it was just a coincidence.
All in all, I think I'm in better shape. If I see issues with these new batteries, I'll start digging into the Magnum's settings.
Thanks for everybody's advice. It's greatly appreciated.
