I had a Viking that would not stay on the selected stitch; Went back and forth with the dealer for about 6 months, wrote to Minnesota and finally got my money back and returned the machine.
Never another viking for me-got an Elna that was a workhorse for many years, worked and worked and worked. Now am using a Brother QC 1000 and a Babylock Elegante 2. Oh, and a Singer Featherweight. Love them all.
Good luck and I hope you get the results you want and a machine that will work for you.