Batter back swing hits F2?

[GeoCBlu]

Have had two sit's recently (Fed ball) where catcher has been hit by the back swing of batter usually due to batter letting go of top hand on bat. Catcher was in his proper position as was batter. In only one of the cases was catcher making a play on a runner stealing and was unsuccessful as a result. In the first (no play being made) plate umpire made no call. In the second BR was called out and runner was returned. In the second F2 was hurt pretty bad.

Tried unsuccessfully in either rule or case book to find specifics on issues regarding "back swing" so assume it is the same whether you interfere with catcher period if catcher is in the process of making a play. Most of our discussions surrounded the issue of protecting F2 from physical harm and whether batter is responsible for controlling their back swing in all cases or only when F2 is attempting a play. Would love to have some help here especially if you have any references that can help.