[BUG] Faction selection

To reproduce:

• Click Skirmish from the main menu
• Click Next
• Choose any faction
• Click Next
• The faction you have chosen is not among the options for opponents (can't have double kingdoms)
• Click Back
• Choose a faction other than the one you chose last time
• Click Next

Observed:

The faction you chose the first time is still not available as opponent, but the faction you chose the second time, is.

Expected:

Both times the faction that was chosen should not be available as opponent.

Workaround:

Go back to the main menu and choose Skirmish again, now the faction you choose this time is not available as opponent.

Addendum:

It seems that when you add a faction, then go Back, then choose another faction things go wrong as well, but I can't determine any pattern at this moment.