The error is a CR motor overload which just means the printer tried to move the head but didn't receive feedback that it actually moved. Most CR motor errors are caused by head strikes and/or dirty encoder strips. Since you heard a bang, check around the head and motor/drive system to make sure there isn't anything physically stopping the head from moving freely. After inspection, with the machine turned off, move the head back and forth. It should feel smooth with very little resistance.
If everything looks and feels good physically, clean your encoder strip and sensor. Clean and grease the rail if you haven't in about 6 months. If the problem persists, you most likely have an electrical issue, encoder damage, and/or encoder sensor failure. If the problem goes away, it was most likely a fluke/electrical fluctuation that the printer did not like.