Bumps

I recently got my tires rotated and now I have a problem when I go over any bump. It sounds like a skid or a like something rubbing. I took it back to Allen Tires where I got the rotation from and he said everything looks okay, but that the spring coils are rubbing against the bottom plate that holds it in place. He sprayed some WD-40 on it and it went away, but once the WD-40 dried up I got the noise again. Has anyone else had this problem? And if so, how do you fix it?

Thanks.