- Long time use and abuse and the pickups wear out.
- Careless removal of pickups and using improper tools.
- Moisture and humidity that can cause the parts to rust or oxidize.
- The strings to get snagged into the coil or bobbin by picking hard.
- Removing or replacing covers with ones that don't fit properly.
- Using unsuitable replacement parts.
- Damage to pickups when they are installed improperly.
- Cold solder joints.
- Glues and adhesives that can oxidize and break the magnet wire.
- Epoxies used for potting pickups can shrink and break the inner wires.
- Magnets can get degaussed or demagnetized or put in wrong.
- Removing pickups or pickguards from an instrument before removing the strings.
WRITTEN ON JUNE 12, 2015, BY