Hi. So I checked the HDRi - nothing wrong. I set Z rotation to 0 (world coordinates) - nothing changed. Checked (again) if CoronaCameraMod was set to Spherical - yes it is!
So in the next test I made a spline-sphere centered around the camera (Blue lines are 0, 90, 180 and 270 degree, and red lines are 45, 135, 225 and 315 degree). As you can see in the attached render, there's clearly missing a bit of the panorama - about 60-70 degrees.
Any ideas?