V3 Masada PTS -

My issue is... I put in a new mag.. put it on semi auto...
First 5 to 10 shots.. the FPS is next to nothin.. BBs shooting 20 ft.
then it cures it self and starts shooting Normal perfect high FPS.
when its shooting low fps.. i notice the piston is hitting hard../slapping
so.. im assuming Nozzle isnt fully connecting with the bucking.. and
all my air pressure is just shooting out everywhere else. but
IV had my gearbox open.. so many times now.. even made sure my tappet
is indeed got full range forward motion and my Tappet spring has been
changed to a stronger spring... but can stronger spring be bad?
or cause this.? I've also short stroked my piston along with sector gear. but i dont see that being connected to this problem. So agian
It shoots like shit... for first few than change to Full Auto.. and then back to semi again and It has the Normal high FPS again. Im lost. Thanks.
( and I've revolved through 3 different buckings.. with different hardness degrees and nothing changes. )