I would try another dealer. Berninas are wonderful machines. I have had them for years.
Sounds like the computer needs reprogrammed or something. My Bernina (I don't have a 830) feet have numbers on them and the machine picks up on the number. I woul even contact Bernina, I'm sure they would do whatever is necessary to make your machine right. Even if they have to give you another machine. Do not give up.
Get on the phone and make some calls until you are satisfied. My husband always says 'the squeaky wheel gets the grease." LOL