Timurids stuck bug

[oz_wwjd]

I have a problem in my current game,where the timurids are marching between one of my heavily Fortified cities and the map border,back and forth every turn,all 8 stacks of them. They've been doing this even since 2 of there generals attacked the city and were repulsed,with heavy losses. How can I get them to attack,without provoking all of them at once,as it is getting slightly annoying. I suspect the problem is that I earlier defeated 2 timurids stack and now they are stuck behind the cities I am defending,with no way to re-joining the horde,without attacking my cities and being destroyed on said city defenses.