Could be a number of things with the TT33.
Try these:
1. Remove and clean firing pin, firing pin spring and firing pin channel in upper receiver.
2. Remove the fire control/hammer group and disassemble and clean it (it is very simple, there are youtube videos to guide you through)
if those don't fix the problem it's one of the following most likely:
1. Your firing pin is worn and you need a new one.
2. Your hammer spring may have weakened and needs to be replaced.
Or it could be both.
And you will also notice that it's usually cheaper to just buy a whole new TT33 and cannibalize it for parts than actually trying to find and pay for parts on their own.
IF anything ever goes on my TT33 this is the route I will take.
The surplus ammo is almost never the issue. The gun was designed to eat that stuff up from the ground up.