Lens Shading in Pro 1?

I have noticed that when I take indoor pictures in Auto mode and the flashing going off, I see a small shadow in the bottom of the middle of the picture, is this what is called as Lens Shading? This happens mostly when the lens is set at its widest position. Is this an inherent problem with the Pro 1? Thanks in advance.

It can and will happen with the on-camera flash. This happens even on cameras like the DRebel, 10D and 20D when using the on-camera flash. I cannot use the on-camera flash with any lens I own except the 50mm.

While it can be a problem, it is something that can be delt with by using an off-camera flash like the Canon 420EX. It works well with the Pro 1. This is a problem that is shared by a lot of cameras. Some can be seen without lens attachments some can be seen with no lens attachments. Even the G-series has this issue with the built-in flash shadowing in the lower right due to the lens ring.