Bots have a tendency to run into walls when on horses and stick there, you can see it occur in tournaments for example with all of them getting stuck against the edge walls should they be lead there. I am unsure of any way to stop bots from this behavior.
Also the eventual dismount when they can't move is something coded into ni I believe, so a Dev will have to explain/clarify on that topic.
Also the eventual dismount when they can't move is something coded into ni I believe, so a Dev will have to explain/clarify on that topic.