In the image you can see I can do 26 damage from ranged attack to the nearby swordman. I have the Oligarchy SP. I'm not sure but I think the bug is only in the damage number shown (26, instead of 10, the max health points for units) and not in the combat mechanics algorithm.
I've also attached the savegame.
EDIT: Removed the savegame because I'm near the quota limit
I've also attached the savegame.
EDIT: Removed the savegame because I'm near the quota limit