Joe, I don't know if it will help but I remember something about the 66, 99, 185 have a "feed raising bar" which has two rollers. While the machine will sew when they aren't rolling, they really are supposed to roll. Seems like I found out about them on yahoo groups but don't remember which one.
How close to the front do the feed dogs come? I just looked and my 99-13 comes about a little less than 1/32" in the front when set on the longest stitch. Is something preventing them from coming all the way to the front of the needle plate?
Janey - Neat people never make the exciting discoveries I do.