Can't say I'm surprised to hear that, But am sorry for your troubles. I too know how frustrating it can be to spend thousands on these kinds of equipments, only to find they're made by some back alley swindlers looking for the fast buck. I had that happen to me with a company called DRS. they pose as German to try and mirror companies like OKM, but in fact everything is manufactured and designed in Turkey, they just have a German guy in an office in germany doing the talking, everything was total junk, I spent about 9,000 on 3 different scanners.
I've owned OKMs too, Rover Gold model, EXP4500 and EXP 6000 Professional Plus too, which is the best scanner they offer, at about 30,000 Euros. and after everything i've been through with all these equipments, I have to say I favor using a 300 dollar metal detector. I have found more clues, and more questions have been answered about my sites with a metal detector, than any of the scanners I've owned.
when I spoke with certain Geophysicists over at a particularly respected GPR company who are mainly focused on Military, Construction, Utilities and Transport Infrastructure, so you know their scanners must be reliable. They had the chance to look inside some of these OKMs since customers would bring them in for re-calibration.... All I can say is for what these things are sold for, and what the company say they can do... These guys were not impressed.
As for taking legal action, i think little can be done especially from here, and it would be a very lengthy process. I would simply threaten to expose their company across the internet should they not take drastic measures to replace your unit with something more respectable looking. That's what I did with DRS and I was given two free scanners. They still were not that great, but at least they made an effort to fix their mistakes.
Focus on the scanners in the sky, that stuff really works.