AutoCAD image moves in locked view port in AutoCAD 2013 & 12.

I lock my viewports in paper space then I start drawing and editing in my viewport.

All a suddenly I will noticed that the image is moving. It seems like the view port image moves out

of the port. I then have to unlock the viewport and pan the image back in the

port. I have noticed that this is worse in 2013 than 2012. What is the problem

here? Is it a program flaw? Is there a way to fix this?

Thank you,

You have an image attached to AutoCAD in Model Space and when you pan and zoom inside a locked view port the image is panning. Is that correct?

Attach the file here that exhibits this behavior.

There is no images in the drawings with this behavior. The AutoCAD port seens to pan on its own.

Thank you,

Are you using a clipped viewport?