A too soft cocking piece can result in the sear indenting the surface when the action is cycled rapidly, I've seen quite a few that showed this sort of indentation.
Too much slack in the fit of cocking piece to is track can allow the cocking piece to rotate slightly as the action closes so that when the trigger finally breaks its from one corner rather than straight across.
The surfaces should be parallel to each other, otherwise more pressure of one side induces rotation as the sear slides down the surface.