Hi everyone -
Monumental update! It's all resolved.
I found and repaired the cutoff issue. It was simply trace damage in the PCB right at C26. I bridged it there and it worked. Bob, I tested it in manual mode as well and it check out. Incidentally I was able to calibrate the 367 all the way through each test procedure.
Most importantly the TC memory chip was faulty! That was the cause of the patch issues. I swapped it out with another one I had here and all was well.
I swear I thought I was going mad. I didn't think my build was that bad!
As always, thanks for all the help everyone. It's greatly appreciated. (And thanks for the repair offer Johannes! Another time!)
Have a great day!