With all electronics...TV's, computers, modems, heaters, sewing machines...a Hard Reset may help when there has been an unexpected interruption of some kind will fix the error.
You want to unplug the appliance/machine from the wall or surge protector and wait about 20 minutes. Don't just turn it off, unplug it so no electricity is going to the item at all.
With any item that has any kind of interrupt protection or circuitry at all..these things have a memory of sorts. If you have a problem with the bobbin or broken needle, etc....and you have done all you can and still have the error...the machine is remembering the last thing it did (error, heater tipped over, etc)..the Hard Reset allows the memory to clear out and "forget" that last event. Unless there is a real damage or the problem has not been cleared...the hard reset will put all right again.