Of course I meant Dugi Arrow whenever I wrote taxi.
I did some more tests around the cave and confirmed that I have to stand on the ground in order for arrow to function properly. This means that once I step on any part of the case inside or outside then Arrow get confused. Standing on the stone ground just outside the cave entrance is no problem, though, but the first step on the stone ground of the entrance is.
This goes so far that I can step sideways to make Arrow change its behavior (instead of forwards or backwards, as long as that means stepping on or off the stone ground.