I am very glad to hear that you found the source of the problem.
I have been busy, and haven't been on here for a few days. Reading the posts, everybody that knew anything about something wanted to help. Of course we all want to help.
There were a few posts that suggested looking in the wrong place, but oh well, that doesn't matter any more. We were at a big disadvantage with not knowing the complete system and trying to solve it via the internet. Even with two electricians on site it was a big mystery.
If you ever have to resort to to finding an electrical problem by disconnecting or taking apart the system, keep a few things in mind. 1) Start at the Source, The head, not the tail end and test it as you go. 2) Split the system if you can, e.g. AC from DC and panel #1 from panel #2, and so on. 3) Compare the working to the non working and find the differance.
Now Life should be better in your world!