kde drops temporary file edits there i believe and forgets to clean it when done sometimes, worst thing is they take priority over the files in ~/.local/share/applications/~/.local/share/applications/ or cause double entries :clueless:
hmm ok only thing i can think of then is take the Exec line from the desktop file and try run the command directly and see if that works (without the Exec=Exec= part) unless you already tried that and i missed it