Much needed update
The rig started having the same issue once again shortly after posting the last update. After replacing battery cables, tracing cables, tightening cables, etc. We finally discovered the issue and repaired it.
The Battery Control Center board was burnt out from the initial electrical surge from not having house batteries in during first trip. I found a replacement board, brand-new from Leisure Time Distributing. The board I had to replace was:
INTELLITEC BOARD FOR BCC 73-00635-000. Installation was incredibly easy, though time consuming. It took maybe a total of 20 minutes, and most of that was reassembling everything.
Thank you all once again for the tremendous help with this issue! All of your suggestions help lead us to the right problem.
Hope everyone is well!