To be honest, I don't think my usual dealer or other dealers here would let me have a keyboard who's not working
as supposed for any long.
It's not only the factory, it's also the dealers reputation who might be damaged and bad by let customers suffer.

I agree in Diki's words regaring to try sort out if i.e. a mirror of Dom's HD would make Tony's Audya work in the
same (stable?) way, or if he manage to trigger the same faults even if replaced all data.
If so, you surely should look for hardware failure.

Too long time without any action and agreements about how to solve or in worst case reverse the deal is not any
good for the case I guess?

Cheers
GJ