My Gate Won't Shut! WT#!

I sallied against the Timurids and before they could get to my gate I got my artillery in and then all my infantry. (sucking them into my cannon tower fire) But my gate wouldn't shut. What the heck is going on or what did I do wrong?

make sure you don't have any stray soldiers about. a single man jammed by a small path bug within a certain distance on the gate can hold it open for them to swarm in from. Also, make sure your men have some distance from the gate too, even if your units clear the gate entirely, they may still be within the "can't close" zone. Also, if you have spill over people from putting em in the little gatehouse section of the wall, that sometimes seems to do it as well (usually because of what i first said)

Also, a possibility is that there is an enemy spy in your town and he has opened the gate. If so, nothing you can do about it.