I can imagine maybe they had production problems, and they're in the "we'll get around to it" category - and either actually fix them, maybe make them fleet cars, etc. or else maybe cannibalize if it is determined not worth fixing. I can't imagine what would put them in the "not worth fixing" category - but similarly, I can't imagine why they'd keep a car there for months if they could possibly pull some parts from the assembly line and swap out. there has to be more to it. my pocket theory is maybe they use certain chips or controllers or parts and they're waiting for them to come in, but yet again, i have to imagine the computer is maybe a few thousand dollars, so swap out with a current one, and then use the "bastard lot computer" in a new car when the chips come in.
We can agree the customer service (or lack thereof) is atrocious, but this is NOT a stupid company, far from it, so there must be some sort of sensible reason why those cars have been there so long.
I can't detect the reason, but there has to be one. There just has to be!