I've had two copies of the 70-200f/2.8 L IS II, first copy went into the Ocean off a Boat attached to a 5DMK2 (I think this goes under Operator Error/stupidity), now I have a another unit that I use on my 1Dx/5DMK3, neither unit has had this issue, but, My 200f/2 L was making this exact same noise when I first received my 5DMK3 (wasn't an issue on the 5DMK2), When I received my 1Dx it wasn't an issue on this Camera, only the 5DMK3, I eventually sent it into Canon Singapore for new Firmware ?? Came back Ok no noise. Definitely an IS issue, from the Posts though it sounds like it can be an issue at any time during the Lens life, I always check the lens in the shop prior to walking out the door, but would seem this is an issue that could generate immediately, or over time, considering it's such a damn good Lens & not cheap, bit disappointing.