What wall bug?
Sometimes, even if you tell your units to attack the wall, so they can push through and go for miners, etc. they will instead stop attacking wall and attack a single spearton in front/on the wall.. IT is a hit box or some other error/bug, and is a PITA. Easy to abuse, since with 3-4 spears, u can easily push through a wall and force opponent to garrison or lose lots of miners. But the bug means they stop attacking the wall, and attack the spear, bunching together, so taking more CA damage, and allowing them to get more units out as well, like a 2nd spear, etc.
PITA.