Problem with alpha channel on Windows desktop icon

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

Not sure what the problem was, but reloading the .png files into Xojo solved it. Why it worked on Mac but not Windows is weird.