I'd second the call your district rep's constituent office to see what's up. They usually have a case worker or department contact who knows how it works.

Idk about ANCHOR, but my car is co-owned. I got it in college, my dad put his name down as a co-owner when documents were being made up. Anyways, whenever I do registration I have to get him to sign. They've rejected it when it's just my signature even though I'm the primary owner and he has his own car. I could get a title change, but with MVCs being the way they are it's just quicker to tell him to sign and move on for another year.