The flop tells you that the top arm of the frizzen spring is not well shaped. When the toe of the frizzen comes down on the arm of the frizzen spring, after the frizzen pops open, both the toe and the heel should be sitting on the arm together, so there is no flop. The arm needs to be bent to solve this problem. Not all " gunsmiths" know how to do this, or want to do that kind of work on a spring. It makes everyone who does nervous, too.