This has happened with 4 different students now. I try to invite them to a course, but then the last stage of "Add People" where it says "users are ready to be added to the course" will list the new invite's email address as already being associated with another student's name. There seems to be no way to correct this. Even removing both students from the class and starting over doesn't seem to help.
Has this happened to anyone else? What is the solution?