Not to throw mud into the water, but if the dealer is wrong who will eat the cost of the new PCM? Not saying they are wrong, but a on again, off again short in the PCM seems like a WAG to me, unless they plugged it into some tester and saw it actually happening.
I like to use Corrosion-X spray on electrical connections. I would spray the connection to the PCM with it, and then chase done as many input connections as I could and spray them also. Easy for me to say that while I'm sitting here in a S&B, it's a whole different story when you're on the road with limited resources. Good luck.