My Sweet Sixteen is just over two years’ old and has had a decent workout (nearly 9 million stitches and counting!). When I took it in for the light ring change out a couple of weeks back, I noticed that the top spool holder was loose. The thread seemed to be stripped from the screw-in part. My rear thread mast was fine, but my dealer did say that she knew of some that were also a tad loose as the thread seemed to be stripped from them.
My solution was a $2 roll of plumbers’ tape from the hardware store! I think I have enough tape to last several lifetimes as I only used a tiny bit to wrap around the screw-in part of the top spool holder, and there seems to be an awful lot more on the roll.
It worked beautifully. The top spool holder is now firm where it screws in to the machine–no more wobbles!
I also put a tiny bit of plumbers’ tape on the thread mast screw-in bit too, just in case.
Rhonda Bracey: At Random 
Good info but it amazes me the “fixes” the HQ SS customers have to come up with to compensate for poor vendor quality!