If you select the control for one player slot you were abel to switch the list box through all possible controls in both directions.
Now you can select "human" only when you switch to the left. Is it a bug or a feature? Its not really intuitive in my opinion.
Another idea how to handle the "human" switch:
We are doing it the same way a network player chooses a slot, beside the fact that you can switch to every slot.
Control list box is fixed to human and non editable in this case. All other list boxes cannt select "human".
