Gaeckle is on the right track.
Your springs do need to be balanced. By this I mean that the frizzen spring should be just enough to hold the frizzen shut, absorb the stroke of the hammer, and then flip open and stay there.
This is hard to accomplish.
I have spread a frizzen spring until the frizz needs two hands the shut, and STILL the main flips it open with such force it rebounds back, chipping the flint. My next effort will be to weaken the mainspring by grinding thinner, or make a less powerful one.
Don't wait for the results, it's going to be a while.
Can someone explain by words how lock spring balancing is accomplished?