Fx impact mk2 gen 3 high pressure regulator and wika gauges Problem

Hello

I set my regulator 140 bar wika gauge. After 10 shots the gauge shows 130-135 bar. I went to the range today shot a tin of slugs 140 reg 1035 fps. After 400 shots reg was 130 and velocity 1015-1020. And one other think i noticed after the 10 shots and reg goes down when i fill the gun again to 250 the reg goes to the same place.

You think if i upgrade to huma power hammer spring to hit the valve harder will fix the problem?

Can you pls help me

Thank you