FX Panthera ,? Has anyone had this issue?

I have panthera. 700 with 600mm barrel. At 150bar my fps drop Like hammer is not opening the valve. I have 26 gram hammer,and blue tuning spring. I tried 20gram hammer with oem spring,and tried 13 gram hammer. At 150 bar my gun shoots 60gr atp slugs 888,but if I try to go up on reg it slows down. Spring tension maxed. Why will my valve not open past 150 bar? Done exact same with all weights and springs ,past 150 for some reason fps drop like 100fps,but as tank pressures decrease the fps raise up 5 to 7 fps a shot, any ideas or if you know why please let me know. The slugs um shooting seem to shoot better faster. The 49.5 gr atp slugs cut a hole at 100 yards at 974 fps. Also my first shot seem slow most time after sitting a while.
 
that's a nice hammer weight, I use a 12.8 gram hammer and the 160 bar regulator setting opens fine for me at 3.2 micro and I also use the original spring. I have a panther 600 but with a modified liner from 700 so that I don't have Chok at the end

if you want to shoot a 60 grain ATP slug, you need to go to a pressure of 170 bar with the original liner for the 700mm version, i.e. for the 600mm version go up to 175 bar
 
the panthera is still sold with the original stem valve which is thin and bends immediately and then either starts to leak air or doesn't work as it should.
IMG-20240519-WA0002.jpegIMG-20240518-WA0021.jpeg
that's why they started adding a stronger stem valve to the dynamic version, which already holds up well

I don't have a photo of the new version
 
the panthera is still sold with the original stem valve which is thin and bends immediately and then either starts to leak air or doesn't work as it should.
View attachment 468823View attachment 468824
that's why they started adding a stronger stem valve to the dynamic version, which already holds up well

I don't have a photo of the new version
I'm sure my gun has the big valve. The seller would have not sold it to me other wise.