I never thought wall breakers got knockback since they are tier 2 troop. You can clearly see the wallbreake getting knocked back by the mortar shell. Wall breakers should be immune to the mortar shots like the giants and wizards.
Guess there is another thing wrong with wall breakers along with them not doing damage to clan castle troops..... I made a thread on this a while back.
http://forum.supercell.net/showthrea...-castle-troops





