I used GIMP to create an icon for the desktop app I am working on. It is essentially a circle on an alpha channel (transparent) background. I saved it as a .png file and dragged it into my Xojo app. It looks fine in the Edit Icon window with the corners of being transparent. But when I build the app and create a desktop shortcut, the corners of the icon are white instead of transparent. This only happens on Windows. It works as expected on Mac.
There was a similar issue back in 2017, but the cause then were old icons.
Windows Icon editor doesn't pull alpha channel from PNGs with transparancy