This happened to me too, the trigger bar has found a way to get under the retainer in the FCG when the Safety is activated in single action. I sent it back to FNH USA today for repair. It happens in the middle of a course of fire for me as well I put it on Saftey and holstered then when I drew it back out the hammer wouldn't drop and the trigger was locked up. I was able to re-create it at home and send in the summary with the pistol for repair. I will update when FNH gets back with me or I get the pistol back.