The following is a phenomenon I have seen a few times in different scenarios. The screenshots are from GB06 Three Times is Not a Charm.
This first screen shot illustrates W Smith’s four-regiment brigade deploying into column formation.

This second screenshot illustrates the same brigade in column formation with the centre row containing two regiments.

This third screenshot is the brigade starting to form a battleline – the centre row is separating into two regiments.

I have been unable to determine any commonalities during the various times I have seen this phenomenon. For instance, no other units (friendly or foe) are nearby.