Has anyone ever had an issue with their 17mm f1.8 clicking loudly? It only happens in CAF in movie mode, set at P priority. The clicking is really loud, and is either from the focus motors or aperture motors. It basically overpowers all the audio in the video. I've already sent it back for warranty and all they did was open it up, clean and calibrate it. When I got the lens back, it seemed to fix it, but now after a couple weeks, it is clicking loud again. I've only had this lens a couple months and it didn't do this when new. Any ideas? Anyone have this issue? Thanks!