My son cannot enter any created world once he creates it; he must sign out and sign back in first. He is on an Xbox One S as a Family member with some limited access under parental controls. Once created the new wold is greyed out and inaccessible until the sign-out and sign-in process is completed; this is the same for pre-existing worlds. This was also true for his sign-on with 1.8 and continued with 1.9.0.