That's a computerized machine, right? One thing I have learned (from bitter experience, believe me) is that computerized machines sometimes get wonky for no apparent reason. At times I have to turn off my Singer Quantum L-500 and just WALK AWAY for a while (before I toss it out the window). Sometimes I think they have to clear out their little computer memories in order to stop torturing us. Once I go back, I always change the needle (because at times needles can get those microscopic burrs that cause havoc) and generally it's okay.