Earlier in the thread I think it was stated that the problem with the 92s was that they were too easily upset by (minor) faults in the ETS for the older coaches.
The parallel I would draw is with the household RCD (Residual Current Device) equipment we were encouraged to use with our outdoor equipment (lawn-mowers, hedge/trimmers etc). Shops got a number of these RCDs returned as they kept tripping. It turned out in many cases that the RCD was not faulty but that the lawn-mower had a minor earth fault.
So I suggest new coaches is what the 92s need. I could, alteratively, suggest that the 92s need to be de-specced to allow for the type of electrical problems that 86s, 87s and 90s are not capable of noticing.
I could be completely wrong and I do think that locomotives that have lain unused for decades (iirc ?) will quite possibly have more problems than brand new un-tested locomotives. So perhaps those problems just need ironing out - but quickly while there are still customers !.