Hi Squinge, I'm having this same problem as Athena with this hack.
Great mod...but there's one problem..
This is the first time I've used this hack, just downloaded it today, and I'm using the EP5 version. I have all the EPs and most of the stuff packs.
I played a YA in my base neighborhood and everything worked fine. She went to class, had a regular job, did her assignments... But then I went to play some of my real uni students in the uni neighborhood and they were aged to adults. I couldn't change them back by setting their semester or changing their major. Their class panel was completely blank, and when I went to the change major screen, all the majors had no names and the associated jobs were gone too. They still had YA voices though.
I ran the conflict detector thing, and nothing came up related to this one. Once I took the hack out, they were fine again.
Oh, another thing, they started out as YAs and had their class panels, but aged to adult as soon as the hour changed.
Was really looking forward to this one, and I hope you can figure it out. Thanks so much!