This morning was the first knowledge I had that a .png file existing as a link to an icon in the same extension was an issue, and they will be fixed at my first opportunity which is tonight. Upstream apps are often known to use symlinks in their default make install for the same file needing to exist in 2 different places, perhaps that is where one or some instances came from as I normally copy when needing to add an icon. Or perhaps the icon somewhere in the /apps/extension/share/icons/ directory was used, where they are symlinked icons as well and is often pointed to by XFullIconPath. But since it is now a known issue, the pixmaps/*.png entries will be double checked to exist as a real file.