I'm sorry to hear about your experience.. and I guess that either I've been lucky, or you've been very unlucky... I'd tend to believe that you've been very unlucky.. which is unfortunate..
I'm surprised Davey, hasn't helped you more as he has been very helpfull in this forum in the past, but as you said he has been ill...
He was probably THE main reason I chose a Mesh in the first place. As I always thought he would help me as a last resort kind of thing...
The guy I spoke to at Mesh support regarding my memory, Amit Patel, was both courteous, and polite... he immediately offered to replace the memory.. which I found encouraging...
If I were you I would give Davey one more try. Explain all of the problems that you have had, along with timescales, and give him a day or two to get back to you, with an offer.
If I had repeated problems like yourself, then I too would expect a replacement machine, and even some sort of compensation, (extra memory maybe) for the inconvenience and frustration.
I hope your problems are resolved by Mesh, or if not I hope you can get your refund quickly.