[Hectic]

You changed too much stuff. And used shs.
deepfire stainless sears in a stock tsd sd700 trigger box on a lalax sp150 worked for 5 years. Now i have the same sears in my tm vsr10.
id say it likely has to do with the meshing between parts.
Just for ref.
all parts pss10/laylax unless otherwise stated.
TM VSR10 pro hunter.
Teflon Cyl.
piston (airbreak removed)
spring guide
sp150 spring (495fps~)
Random sorbo pad
hop chamber
deepfire stainless first and seccond sears.
never had a failure and as i said above all these parts were in my tsd for years before I picked up my TM. And even ran a 170 spring for plinking about 100 rounds (565fps~) you could try dropping the 2nd (piston) sear you have in the stock 1st sear. Its really only the 2nd that wears out. Really tho at those velocities (360fps~) i dont see how the sear even failed unless you have many thousands of rounds put through it.