Everything about the season ending is one problem - some services were restarted on the server during your season ending. I explained this somewhat in another thread and on the league comments:
http://igpmanager.com/play/?url=forum-thread_1/3080#22091
I've added the 100 reputation gain now for the Elite tier winners.
As for the experience atrophy, I'm assuming that was intended for when drivers did not take part in a race. But I don't think this makes sense, especially if it's fast enough to suppress gains. I have
removed the atrophy of the experience attribute in response to this thread.