Have you ever tilted the camera forward and heard what seems to me the OIS shuttering?

This was a mechanical sound that occurred twice this past weekend while shooting hand held from an elevated position in which I was pointing the camera down at pretty steep angle. The sound stopped when I brought the camera back up to a level position both times.

It scared the hell out of me so I turned the camera off, then back on at which time I could not repeat the problem.

Does the OIS have a hard time handling steep angles?

It never has for me. You weren't by any chance near a radio transmitter of any kind or size were you? That's the only time I've had the OIS act bad. That and leaving it on while I do moves on a tripod which Sony warns against.

No, Mike, I was shooting through a window downward at some action 20 ft below me. The window was open and I rested the sun shade of the lens on the window. This contact is what was making the noise so noticeable, I believe.