So after a good amount of hammering and dremeling, I got a Fostech AK Echo trigger group "working" in a PSA AK-104. The last issue I'm running into, is that it's firing out of battery on the echo shot, from what I'm guessing is bolt bounce. The footage above is kind of blurry in slow mo, so I'll need to take some high speed video. The upside of the Echo is that it has an auto sear style lever that only allows the hammer to fall if the bolt has gone back home, but that doesn't stop it if the bolt bounces back out of battery after that. Their support has been responsive, and they're saying that an AK buffer (the one that slides over the operating rod/spring and sits at the back) combined with an added recoil spring spacer (an additional spring that is put in front of the regular recoil spring on that rod) can help. I ordered those things, but I'm wondering if anyone else has run into this and what your experience is so far.

hammering and dremeling ......................

Yeah, PSA has more material inside their trigger guard compared to what's found on a Russian Saiga. The echo trigger can't complete it's needed range of motion with that in place.

Serious question here, is it possible for a real (e.g. not a blow back) AK to have bolt bounce? I don't understand how the bolt would bounce out of battery once the bolt is locked.
I could be completely wrong on this, I'm not an AK expert, just what I am thinking based on my understanding of the AK operating system.

Sadly it can. Apparently the real full auto AKM has a rate limiter built into the trigger mechanism to slow down the rate of fire because of bolt bounce.