[lurkingknight]

ah the dreaded trolley float... I've had it happen on some contact housings with some mechanical triggers. Friend of mine swapped out a trigger in his src because he liked the feel of the g&p trigger better and it fucked it right up. The trolley would fire once in semi and the cutoff would bump it but it would just float on the trigger hook.

This might also happen if you've had to drill out where the trigger post was and improperly tapped a new screw in the wrong position so the trolley resets back to the wrong spot.