First time it happened portal took me to area over 800 blocks away from normal Nether location. Save/quitting and reloading did not help and I had to delete world and load copy in order for the portal to go back to normal. The second time it happened was teleporting from the Nether to the surface world from different portal. The portal should have taken me to base but took me west over 1000 blocks away into chunk I wasn't trying to open yet. Again I had to delete world and load copy for portal to go back to regular location.