I just found this thread, I'm having the same issues here. I have a similar build to Rougaroux22 same barrel, gas block, bolt, charging handle, trigger but on a Seekins precision receiver set.. I am using a Tubbs flat wire spring and a CTS Engineering Aktive recoil buffer. The few times it has locked back, it was caught on the bottom of the carrier, not the bolt face. It doesn't seem like it's getting enough gas back through the system. I'm hoping there will be a successful update from Rougaroux22 or someone soon.