Super Swivels can be negatively affected by movement in the line that is not in the same direction as the swivel is designed to turn.
For instance a straight through swivel that is being jerked side to side (as opposed to just turning) will fail prematurely.
Based on your description I would look at bearings, clamps, etc, as applicable to your swivels, things that hold the lines in place and ensure that any forces being exerted on the swivels are only in the direction that the swivels are designed to turn. As machines break in over time bearings will loosen and wear out, clamps will loosen, etc.