Agreed about what @pajfest says above, it's still happenning to me EXACTLY same thing, not even with reloading script, or changing pathfinder works, it just stucks. The only thing that helps is restarting Tibia client, I've watched diagnostic thing and where it says "Following path:" it's false, somehow it doesn't go ahead, I forgot to take SS or something, I'll be aware for next time..
When this happens my character is stucked with many monsters, those are in way to hunt so I haven't added to atk them, but I have added in spells if walker is stuck do x thing, but when this bug happens, there is no Walker Stuck message, so it doens't atk any monster (I have also atk all creatures if stuck).