Betty,
I have a 2170. Intermittedly, when embroidering it cuts the bobbin thread off too short and then when it starts the new color I sometimes have to stop the machine, pull the bobbin, pull the tail out longer so it will catch, then back up the stitching to fill in what was missed or just start that block over. I am in a lifetime embroidery club at the store in my neighborhood that sells them, and the girl that teaches has the upgraded 2144 to 2170. She said that is a fluke in those models. I have not bought the 4D but would love to have it just for the sake of making bigger designs than the rectangular hoop that came with it. I have the Grand Hoop and am limited to just alphabet when it comes to very large. Would love to have the CV 5.5 someday, but way out of my budget at the time. My 2170 is overwhelmingly great anyway. V.