[blindmanwalking]

Originally Posted by Splute

When I initially see this, my mind thinks in regard to rule 4-27-5: If however a player approaches an opponent from behind or from a position from which he/she has no reasonable chance to play the ball without making contact with the opponent, the responsibility is on the player in the unfavorable position.

I follow your perspective in the initial act of B1 reaching over without contact. I have no call there. B1 puts one hand under the ball. I still have no call at this time; neither held ball or pushing. But in my mind any subsequent contact due to B1's unfavorable position is still on him, not on A1 trying to maintian possession.

But as JR stated. If you see held ball first, call it. Nothing matters after that (except flying elbows, etc. etc.)

I vote for this one.