Email sent with copy of the users manual. In those days they gave more information than they do today.
If venting air, check the seals but be aware that if air pressure drops too low, maybe around 70bar, then the air will vent naturally as there is not enough air pressure to hold the valve shut. For this reason always cock the rifle when filling from empty.
Cheers, Phil
Just reread your post ... 200 bar is too high a fill pressure ... see manual. My guess is that the very high pressure is stopping the valve opening under the hammer blow. Keep firing to bring pressure down to c. 170bar or less and I bet the velocity will increase. Do not adjust until you have tried this.