Mobile Bumped Diffuse problem

Hi,

I am trying out the mobile bumped diffuse and regular bumped diffuse and everything looks ok, but it seems as though I'm losing the bump when the textured object is too close to the camera or when it is further away from the camera and almost off one of the 4 edges of the screen. Am I doing something incorrect? Or is this just a quirk with bumped diffuse/normal maps?

BTW I have only tested this out in the editor. Below, are 2 screenshots showing where I run into the problem. The top is bumpy and on the bottom shot, the camera is just nudged over a tad and the bump just disappears.

Thanks