This seems like a really obvious one to me, and i looked through the obsolete lists and couldn't find it, so, here it goes..
If I make more than 1 trickery tower, only 1 of them works to have conjure on autocast.
In a multiplayer game I made one and not even that one tower that I had did it automatically, so i'm ~90% sure somebody else had one and it will only allow one tower on the entire map to actually conjure autocast - others must use it manually or the tower will not use its ability.