I have suffered of & on from a bad flinching problem for the past 35 years on clay targets but I have never (that I know of) flinched on any game targets. I've had long periods where it is not present but it always returns.
The only temporary cure I've found is to lay off the shooting for a month or so & sometimes I can go for a year or more before it returns. I shoot 1200 fps 7/8 oz loads in guns of around 8 lbs almost exclusively for clay targets so I don't think the flinch is recoil induced.
I once flinched in a game of horseshoes (a game I seldom play) & was unable to release the shoe when I intended & I came close to braining a bystander. Since that flinch was on muscle relaxation rather than contraction I never tried a release trigger.
