Based on looking at the floor, it looks like the stack has 5 options, left/right/forward/backward and stay.
I expect the stack always has a destination, and is looking for a path to get there, one step at a time.
I'd start with that and watch it for a while to see what develops.
After watching for a while I would probably want a way to assign priority and to keep select paths clear, maybe some express lanes or variable speeds.