@tincow77
Think about what you are suggesting.
I assume you mean standing with your shield raised while you turn in masks to prevent yourself from getting attacked / dislodged and having your turn in timer disrupted?
Well, for that to be effective, your character would have to have their back turned to the turn in station while they are standing facing outward to defend against Attacks, as they must be facing the machine to turn in.
I suppose theoretically you could have your shield raised between you and the machine as you deposit, but your back and sides would still be exposed.