SC4020 Getting "Prefetch Page Failure, Failing all outstanding requests"

I'm receiving the error "Prefetch Page Failure, Failing all outstanding requests" about 30 times times a second for 3 seconds at an interval of about 10-20 minutes, it occurs on both controllers but at different times. Both controllers are running version 6.7.22

Does anyone know what could cause this and how to stop it from happening?