This may be a feeble attempt to cure the problem of the residual inertia of the ball on the rebound cycle. Where the inertia of the ball tends to keep the ball in position to restrike the valve stem:
A light duty spring would be placed as shown. The illustration shows the position of the ball durring the firing stroke of the striker. When the steel ball contacts the valve stem, the stem will push the ball upward and along the angle to compress the spring and seat proudly in it's pocket. The ball centerline (green) is off center of the valve stem face enough so that the stem flat face continues to make clean contact with the ball but will instantly align the ball with the stem centerline via caming effect of the ball raceway angle therefore compress the spring.
Now the ball is pinned in its pocket, the striker moves forward, opens the valve and rebounds with the ball still held fast in position.
But the striker has to stop in order to return to restrike the valvestem. When this happens, pressure of the valve stem to the ball is removed. This creates a small window of opportunity. Instantly the spring should, under the force of compression and the favor of gravitational force on the ball, propell the ball to position A.