So if I understand (and if is like an old case I had), you select a player to sub, so this appear in the field, but who u wanna sub'( that s as no-posible to use sub' list) have a red, so dissapear.
As the substitution is not completed, but the player you want playin apear in the field, and who have to go out is with red card, you, can not undo action.

If is that, I had same problem time ago lol.... nothing to do as far as I know, because you can not move again the player with red that is in the subs' list to the field, to use, the player that is in the field, and use this.... complicated LOL