An existing project file can sometimes silently change from spherical
to cylindrical projection. This happens after opening a saved project
file, opening an overlap region in the stitched image and changing the
focal length, barrel correction or falloff correction while the overlap
region is open.
The panoramic image changes from spherical to cylindrical, but the
panorama is still marked as spherical projection. If the image is
subsequently exported to a format that accepts spherical projection, it
may display incorrectly.