A unit can only have 2 formations (hence the max 2), the problem with the two you have used is they are both special ability formations (you need to click the button). AFAIK you can't have both on a unit at one time (though I could be wrong), and as none of the 'default' formations have been used (horde and square) I think this is the cause of your crash.
Try removing phalanx and activating square, save, then see if the game still crashes.
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