I think this one has resolved itself.
Numerous discussions over a week with the vendor, he gained education in some basic operational tests from me. Thus armed, he managed to track down the problem and apparently fix it suitably. (It was as I suspected, a faulty/damaged CAS.)
So then he calls me back, happy as Larry that it’s fixed, now he wants more for it. Well, hopefully someone will pay him more, but it’s unlikely to be me!
