The first link is to the thread long ago. The second link is to several files on the Jiffy Splices.
Take a picture of the front run bay. There is probably a large box and a small box below the driver in the outside bay.
The little box has two sources of power that reach it. One from the chassis batteries and one from the engine batteries.
Tighten all of the connection on the large nuts that you see in there. Clean and tighten everything in the battery compartment.
IF it is possible to get a voltage measurement or two when it acts up you can sort it quickly but you need that schematic of course. Did the one I posted help?
I have a ton of files and schematics for several years that you could download.
There was a few problems with some "chassis splices" in the early 2005-8 year ranges
They build the main harness and then add whatever model is being built to each end.
The battery cables are spliced near the rear of the coach and up front. These splices have had issues. I believe I was having some of your symptoms but not as severe many years ago.
Chasing those things down was difficult but I took them apart and made sure they were clean and tight and then ran copper wire stripped of insulation around the connectors and to the wire at their ends. I soldered this. Hard to explain but they will never give e a problem for sure.
I will find the pictures and hopefully the reference to the splices.