I purchased a Nano Stream 9045 and have been using it for the last two weeks. About a week ago, it started making a racket at startup. You can see the drive assembly and impeller moving in and out while it does this and it sounds like the impeller is hitting the plastic. It will usually stop after a while but it seems to be taking longer and longer before it runs correctly. Sometimes, I have to turn the powerhead on and off a few times to make it quit. I removed the cover and slid out the drive assembly. The shaft is stainless steel and seems very securely attached. Any ideas? My Tunze 6000 on my TS007 kit has been working great for several months. I would like for this powerhead to be as quiet and reliable as it is.