This bug has been reported too many times, and never answered! This happens to me 2/3 of the times, usually 1-2 hours in the game, its very annoying! Seems to be dota-engine related bug, as it also happens in dota, eg teleporting "outside of map" with AM for example. The worst thing is, all controls are disabled once you get "Stuck" (under the world map), and can not use even teleport back to base. I suggest fixing it by allowing to teleport back to base, or automatically teleporting back to base if detected "under the map" stuck condition!