I'd check to make sure that I've put my foot all the way down. I've done this and its taken me a while to figure out why all the foolishness was happening. :O Then came the DUH!!!! When I FMQ I put my feed dogs down. Leah Day admits that she doesn't do things according to how the manf. has instructed and she is not responisble for any damage caused to your machine by using her method. I don't think I'd take the chance and maybe voiding a warranty for miss use. I'd follow what the manf. has suggested.
I have a 6600, but very similiar to the 7700.