The default formation for mercenary -guard / -crossbowman / -crossbow is the Infantary formation but should be II = Archers.
Changing to II only last for the session. After exit and load it's infantary again.
Summary:
How to Reproduce: Just hire or upgrade to the unit.
Quest/Settlement Name...
The Northern Light Harness seems to be too small to fit to a horse.
Screenshot:
Summary:
How to Reproduce: Just equip the harness.
Quest/Settlement Name (if related): ---
Media (Screenshots & Video): ---
Version: Beta 1.41 but I remember that the problem was also in 1.30 and 1.31
Installed...