you should check that with the trigger pulled and held back(like at time of firing). the hand opening in the frame can become enlarged, the hand can have wear, and the ratchet can have wear, also center pin, bolt & bolt engagement recess(if your model has a bolt), wear can cause this. seldom is it just one thing but instead wear in all areas. anything can be fixed but sometimes you have to ask Why.
Just walking on the edge of of my grave.