This one popped up after the last Steam update a few days ago:
When I attack a party and they decide to fight in a wagon fort (or whatever that wooden barricade is called), after the enemy's numbers diminish and need to respawn, my additional forces respawn (twice!) instead of theirs. So the battle turns like 100 of my troops and 15 of theirs, and ends quickly.
Long story short, enemy never gets reinforcements when in wagon fort.
Not used to be like that before the last update.