I've had my 5D MkII for about 2 1/2 years now, and a few months ago it inexplicably quit locking focus for me. Nothing happened with the camera, have been using it like always - no damage, etc. Just started realizing that when I focused on an area, then re-composed, it wasn't holding the original focus point. So I turned on the focal point setting so I could see during and after a shot where the focus had been. Any time I focus/recomposed, the focus was never on the original point of focus.
I've read my manual thoroughly and can't find any settings that may be causing this, so I'm really hoping it isn't a camera malfunction. Thoughts?
Also, I am no longer able to set my ISO at 100. The lowest I can set it is 200.
With both of these issues, I welcome and greatly appreciate any thoughts, suggestions, or similar experiences.