I set up a Custom Championship with all the MOD tracks and now with the update V1.5.5.2 I can't access this Championship, as a few of the MOD tracks have bugs. I noticed that you can't delete a Championship that you set up. All you can do is modify, but I can't even go into that particular Custom Championship due to the bugged tracks! The PC just crashes. BTW, tracks that are bugged for me are Brno and Circuits of Americas, but may work for others. They result in ghosted safety car in the middle of the track and car behind garage door in pit. I also have no menu items such as finish sessions, qualifying etc, so have uninstalled these tracks through AMS2 Content Manager.
Try to delete the file directly in C:\Users\Utilisateur\Documents\Automobilista 2\savegame\.....\automobilista 2\singlechamps