If this customer was serious about not liking their elevators down, they would've already modded a couple of them and plan on the other three after the first 2 are done.
Anyhow, I'm not an expert on T4s, worked on a 4 bank of them a bit. I would start by trying to narrow down your issue to a car. Can you take a car out of the group at a time to narrow down which car might be causing your issue? I don't know how they are interconnected if you can completely pull one, or maybe just shut one car off and see if the problem continues or stops
