Quote Originally Posted by mad cat mech
army formations not holding properly when commanded to advance by single click any greater distance than 100 virtual yards
It tends to happen if you drag a box around your units on the field and then tell them to move. Usually not if you select them one by one from the unit card.
I also had it happen when I ordered a grouped unit. The savest way to avoid it is to drag out the formation at the target location.

But what´s worse, this also affects skirmishing missile units, when the yretreat from a closing enemy they often change to this marching (deep) formation.

Talking about skirmishers, it seems they always retreat towards the map edge that was in their back on army deployment. If, for some reason, you had to rotate your battle setup by 180° the skirmishers will move towards the enemy once he is in skirmishing distance.