I find the clip inserts are a real pain, they never seem to be a perfect fit and I've lost a couple. The older versions didn't have them, you had to change the clips to match the rack, an extra expense but better once done.
What I’ve done is remove the inserts and wrap a bit of insulation tape round the rack tube to get a good fit. It needs redoing now and then, but it's a quick job. It has a couple of other advantages - it'll protect the finish on the rack (or the rack itself over 6 years) and it'll always be quiet.