Don't know if this applies or not.....but I had a mid arm machine on a 10 foot frame made by Grace. The bars were made of aluminum and were made of 5 foot lengths connected in the middle. Over time, I got a sag on those bars so the distance between the quilt and the needle changed over time and I was getting problems with my stitching and tension because of the sag. Just check and see if the bar is level. I don't know what the fix is. I just upgraded to a new machine and frame. I did not have much space to quilt anyway with the short neck machine I was using.
I just looked at the 1600P and it looks a bit like my Viking Megaquilter 1200 which I do believe was a Janome in Viking clothing. Another thought, do you have a stitch regulator with it. The stitch regulator could be having problems too....
Last edited by sewingpup; 12-01-2020 at 03:18 PM.
Reason: additional info