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I finally got the problem sorted. Although I was 100% sure I had checked all the terminals to make sure they were tightened properly, it turns out that one of the connections in the back on the bottom row was very loose - the installers had not tightened it.  It could be tightened about two entire turns with ease, then a bit more with effort.  Since I tightened it, there have been no more issues with the bottom battery bank checking itself in and out, and everything is functioning better, although the two batteries to the left of what was the loose connection are consistently a bit lower than the 2 on the right, at rest or during charge or whatever, maybe with time they will even back out

I think most people I was working with presumed I already understood some things.  Again, I really sort of do, but it escaped me at that moment. It actually dawned on me while dealing with something else, and then I went back to double check connections.  Seems like testing the terminals for resistance was not an effective thing either, I had been told to do that, but it must depend on very precise placement of the electrodes.  Figuring out these systems and getting the kinks out of them on my own in a remote location, with no end-user tech support, and no effective back-up from the installer, is challenging.  I am very grateful to the people at NAWS that have been corresponding with me, and would recommend this approach to others.  Even when people don't understand the question, or their answer is not quite what I was looking for, something they say is often very helpful, sparking another train of thought.  I will keep up with you guys and am enjoying looking at other people's submittals too.  Maybe I will find something to contribute to someone else someday.

I have not been able to figure out how to use the clamp meter as you indicated

commercial electric MS2033C Clamp Meter, trying to follow instructions:  A very quick way to compare the "health" of your battery banks is to use a DC Current Clamp DMM (digital multi meter). DC Current Clamp meters are very safe and easy to use. You set the meter to DC range, zero the meter (DC clamp meter readings tend to drift over time/temperature) and then clip on one of the battery bank string's cables. (just one cable at a time, if you put the + and - cables both in the clamp, the readings add up to zero current --- I.e., -40 amps + 40 amps = zero amps).

If you see an issue (battery strings should be sort of close, but they will probably never exactly match charging/discharging currents--Something like 1/3 vs 2/3 current "balance" or greater, something is probably wrong)... Then you can use the DMM to measure voltage drop.

Again, with relatively high charging or discharging current, in a series string, you can measure the cable+connection voltage drops by placing one meter lead on the negative terminal of battery A and on the positive lead of battery B. You are now measuing the entire cable+connection voltage drop (again, with current flowing through the battery string). And typically, you are looking for something that stands out. You may measure 0.02, 0.05, 0.1 volts drop and find one cable that has 1.0 volt drop--That is the guy you need to really pay attention too (dirty connections, loose connections, etc.).