As smalltown eluded to, the hammer isn't moving back far enough to catch the sear. The pressure is too low or, more than likely, it is the o-ring on the hammer that needs replacing.
Also, just to check the sometimes overlooked, the hammer is installed correctly, right?
Graphite Dangerous Power REV-I
– TechT bolt engine, REV-I & Disruptive barrel kits, Prophecy V2 w/ Empire feedgate, Crossfire SS 68/4500
Maroon and Polished Aluminum Dangerous Power Threshold
– 7th Element board, TechT bolt engine, magnet trigger kit, REV-I PMD, Sly Dual Carbon barrel kit, Prophecy V2, Crossfire SS 68/4500
Black and Silver Dangerous Power F8
– APE Rampage board, VS bolt, magnet trigger kit, F8 gauge, REDZ barrel kit, Halo B w/ Exalt feedgate, PMI 68/4500
Polished Aluminum and Red Dangerous Power F8
– Virtue board, VS bolt, magnet trigger kit, Halo B w/ Exalt feedgate, PMI 68/4500