There is no rule that a natural 1 is disastrous on skillchecks... Well, commonly atleast. Remember you still add your flat skill plus modifiers. You can, in some cases, have a skill so high, that no matter the roll you always succeed.
However, failing by a certain margin can be disastrous.
As for failing an order check, it might simply mean that the unit does not get the order and is left to the reasoning of the local officer. If all other units begin charging across the field, then he might follow suit, if it makes sense.
If they all retreat, then he will probably also follow.
If they are archers, then they will probably start shooting enemies that get close.