To summarise my situation I had bought a new china clone MB C3 Star setup with laptop from a UK specialist company. It was around 800 USD at the time in 2016. I only used it for a few times on my personal cars and when it was approx 1 – 1.5 years old it stopped working putting up some errors on the screen - refusing to connect. Bugger!
There isn't really any such thing as a "good" Chinese mux supplier in my opinion. There is a good reason they are cheap.There are several Chinese manufacturers - some good, some not so good. I have bought two, the first in January 2013, the second a couple of years ago, from two different vendors. Both are still working.
I wish that they had brand-names, etc., but that isn't too practical for pirates...
I think that it would be interesting to know for certain that your Russian contact would readily supply real Daimler mux units to the folks on here - there should be quite a market for him.