It's happened to me twice already.

There are times when I can't deploy in defense by "right click+drag" I can only right click and they are deployed in the initial position.

If you always deploy placing the troops carefully angled instead of just stating where you want them, you should find this "bug".

First time I thought I was misplacing them in the narrow streets. However, yesterday I saw it clearly and spent 15 minutes trying to place the troops correctly. I was forced to place them by default and then angle the troops while the ram approached (I like to place two units of spears in 60º in front of the door, like a "V").