silhouette infusion sets with "split" tubing

My son has been using a medtronic paradigm pump for 4 years and he has always used the silhouette infusion set.  Last week we had a strange problem for the very 1st time.  He had unexplained highs all weekend long, He changed his site 3 times and we were doing injections with syringes.  There were no pump warnings stating "no delivery" or any other obvious problem..  He then needed a new resevoir filled and it was then that we realized that the tubing was split just at the end where it twists on to the resevoir.  I am checking every tube from here on in to make sure we aren't using other deffective ones.  I'm wondering how common this problem is?  Pumpers, check your tubes!!!