Brake booster issue- Dangerous please Help

[mattfrediani]

I had a hot rod shop install all new braking system on my 1970 4wd long bed
I put a dana 44 under it with new slotted rotors and calipers. I did not want to do the brakes so I farmed it out to a good shop. I asked if they cold mount the new brake booster level so it did not look funny. everything was great for about 250 miles. the other day my pedal after i warmed it up was solid as a rock it was binding on something. after i pushed on the pedal hard it gave way to normal.
I then carefully test drove the truck and everything was fine. I took truck out today for another test run and the same thing happened. I pushed the pedal as hard as i could to stop the truck and something went bang and then it was fine again. I popped the hood and found the upper clevis pin that mounts the linkage from the pedal to the brake booster rod was almost falling out due to the half snap ring was gone or broken off to lock the clevis pin in place. I ordered a new clevis pin with a hole so I can install a cotter pin so it stays secure. I also ordered the clevis pin so theres not much slop.. I think the half snap ring came loose and when I hit the brakes the pin may have stuck out and binded in the hole on the side of the booster mount that bolts to the fire wall... My question is is it possible that mounting the brake booster level rather then slanted (shimmed) caused this to happen internally in the booster? or was it most likely the sloppy clevis pin that the snap ring fell off binded? any help or suggestions welcome!