Can hurt others while accessing chest

My niece and I were playing on same server (idr but think she was host) We placed two chests in near proximity to store materials were gathering. Then as we were accessing the different chests somehow she kept hurting my character. I don't remember if I also hurt her in same way or if affected visitors only. We had to place the chests farther apart to prevent it from happening again.

(both were ios ipod touch 4g in survival mode)