Sero Motor Jamming


I have two servo motors attached to an adafruit servo shield on an Arduino with a 5V adapter. These form pendulums as part of an art installation. They tend to work for a few days before stopping. They then need to be pushed to start again. Lately one of them fails to start at all. Now both have stopped. What should I do? The code I am using is the ‘Servo tester’ code which makes them run automatically.