The undo button undoes an event. After you press D, but before you press the player, the event is not yet complete so you are undoing the previous event (maybe the previous pass), you are not canceling the ongoing D event. This is clearly a usability problem on our end. So, how do you think we should change it? I will list some proposals, but feel free to add your own.
Mid-event, "undo" should change to "cancel", and cancel the event.
Mid-event, all buttons except for the player buttons should be disabled. This forces you to complete the event which you can then undo.
Mid-event, all buttons except for the player buttons AND the action buttons on the left are disabled. Pressing a player button completes the event, pressing an action button on the left changes the type of the event which you are in. Thus, pressing the "Complete Pass" button would return you to the default state and effectively act as a "cancel" button.
The undo button undoes an event. After you press D, but before you press the player, the event is not yet complete so you are undoing the previous event (maybe the previous pass), you are not canceling the ongoing D event. This is clearly a usability problem on our end. So, how do you think we should change it? I will list some proposals, but feel free to add your own.