Have your machine cleaned before it gets to this.........

The newer computerised sewing machines have some very sophisticated electronics involved with their operation. Lint build up can  deture "optical controllers" from working correctly. Your normal cleaning may not be enough. Most sewers remove the needle plate and clean the feed dogs, the bobbin case and the shuttle.

This looks pretty normal for a shuttle with the needle plate and bobbin case removed for cleaning. Most sewers keep this in pretty good shape. On this paticular machine, here is what was really going on beneath......

The pictures can not really show the extent of how much stuff was packed into this machine.

Just like your car, you need to have your sewing machine serviced by a professional. Depending on how often you sew, will dictate how often you require service. Do it before you have problems. Every problem that this sewing machine had was corrected by this professional cleaning. If you or some one you know is mechanically inclined, you can probably do this yourself.