Try the following to fix encoder slipping issues:
Check rate measurements to see if they are more consistent than position measurements (perhaps using a drill?)
Try all encoding type arguments in the constructor (see WPILib documentation)
Try tons of different PWM port configurations (including slots other than 0-3 in case one of those is bad).
Use the index wire on the encoders.
Use getRaw() method
Try the following to fix encoder slipping issues: Check rate measurements to see if they are more consistent than position measurements (perhaps using a drill?) Try all encoding type arguments in the constructor (see WPILib documentation) Try tons of different PWM port configurations (including slots other than 0-3 in case one of those is bad). Use the index wire on the encoders. Use getRaw() method