@go-go-go @patdavid
For the moment I would suggest to test the PhF plug-in from my AppImage, and not the gimp-edge PPA, for the simple reason that the PhF version in the PPA is not updated very often, while the AppImage is in synch with the latest stable version.
I have downloaded and opened the corrupted .xcf file with the AppImage, and re-run the plug-in from it, and all worked correctly. Here is the result:
The link to the latest AppImage can be found here, together with instructions on how to install and use it.
The GIMP version in the AppImage can be safely used in parallel with the one from the PPA, because it uses a custom configuration folder and therefore it does not mix with the “normal” GIMP version.
Hope this helps!