Some update. First I like to thank all the people who responded to my posts! It was helpful to make a decision.
Well after talking to the vendor who stated that if something is not working they will exchange it and after 30 days I can return it with shipping on me.
I was inclined toward keeping it and with my curious nature decided to investigate a bit. Took the stock off and almost immediately found that the screw holding the air gauge adapter had been damaged. The hole where the hex wrench supposed to go was rounded off.
Trying to remove the screw was difficult. I had to use an oversized star wrench, forcibly inserted, to be able to turn and remove it, either that, or drill it out.
(Should never been that tight, not a good way to seal a leak, which by the way is a less than optimal design anyway.)
What I found that someone, who should not touch anything similar, tightened the screw so much that the head of the bolt damaged the edge of the counter bore for the o ring where the leak most likely occurred.
So I cleaned the damaged edge as well as I could, and ordered a M5 screw with a larger diameter head that I custom fitted to the adapter.( 10mm ID)
In this way the screw head fits the adapter with minimal side clearance and can't damage the o ring groove so it can create the good seal.
After all this, I got my tanks hydroed and filled and eagerly filled the rifle.
It has been two days and still holding air at 200 bar, so the journey begins....