I don't know why I arrived the top of the sky that is a place JP cant arrived after I teleport my friend , I am not sure , maybe he is using JP on that time , but I can sure that after I teleport him , I thought I will fall down . However it didn't , I even can walk on there , my friend teleport me after that , he actually can do it , he can shout the guy below who is using JP , but get warning later , I think this is not my friend problem , we haven't hack , this is the server problem , I hope GTM can fix it . My friend is _Gozu_
I believe a certain area in the map there are barriers. Your friend probably somehow got above these barriers. Just tell him to go to spawn and come back.