Things that rattle loose:
- Check the three Digital sidecar (DSC) power lights are on and bright green.
- Check the ribbon cable hasn't loosened and is well and firmly seated at both ends.
- Check that the Digital Module is well seated in the cRIO chassis.
- Check that the DSC Relay lights come on when the code orders them to.
- Check the Spike end of the PWM cable with a multi-meter to see that you're getting ~4.9v between the ground and the red wire (if the red DSC Relay led is lit), or the white wire (if the green led is lit).
Digital sidecar could have metal shavings inside, but you'd have to remove to open, clean and inspect for internal damage.