With Juki, the thread cutter is electronic. I think something in the stitch control is sending the wrong signal to the machine. No idea why. When I got my Grace frame, it came with a stitch regulator and I had to select what machine, and was told they were very machine specific. I didn't need one as the machine I bought had one, so I think I selected one for Janome as they didn't have them for any machine I owned at that time. It's probably still sitting in a box somewhere in my sewing room . . .
My Juki2010 shuts off my AC on me. I have no idea what type of signal it is sending, and have not been able to figure out any connection to how I am sewing and when it will do it. My big embroidery machine with all it's electronics does not do it.