regardless of the age of the quilting frame have you attempted to contact the manufacturer at all? sometimes they can be very helpful. they may have a clue as to why this happens that none of us thought of. it should not be falling from its own weight.
as to the skipped stitches, again get in touch with the maker. if they refuse to help or ignore you, tell them bluntly that you belong to a number of online forums and blogs (even if you don't) and intend to spread the negative word about their uncooperation (new word) and defective product. sometimes that jogs them and it can't hurt you.