Fx impact m3 both regs drop within 4-5 shots

My m3 regs keep dropping pressure on the first 4-5 shots. Reg 1 starts at 160 bar by 5th shot it drops to 125 bar. Reg 2 starts at 140 and drops also to 125 bar. Replaced orings and piston on reg 1 , didn’t help. Has anyone else had this problem or might know the cause of the problem. It’s just weird that both regs continually drop until 125 bar. Any help or information would be appreciated.