i have the 6600 and platinum 760..would not trade them for anything! if i could afford it i would buy the 7700. but never trade up!
your bobbin should not be bouncing around..you should take the machine to the dealer and let them run it,to see what is going on.
I only use Janome bobbins. i know everyone has different opinions and experiences, but my friend has an older model new home, and used the off brand bobbins for years, and she had a bad wear mark in the racer, or bobbin holder..had to replace that part. the dealer told her, to use only janome bobbins.
they may look the same,laying side by side..but if i close my eyes and ran my fingers over them, you will find one bobbin is concave and one is flat.
i took all my non Janome bobbins and gave them to a friend who has a singer...