I just got a new 70-200 f/2.8L IS III for about a week. I've been noticing that when the IS is activated and the camera is moved/panned the IS makes a faint grinding noise, is this normal? When I hold the camera still there's a click followed by a whir when IS is activated, I understand the click at start/stop and the whir in between are characteristics of the IS system. It's the the grinding noise when moved/panned that concerns me. It's been over 8 years since I owned the original 70-200 f/2.8L IS so I don't remember much. If someone has the version II or III could you please check for me? Other than that the lens is amazing