Is this Renoise 2.1 related - was this song saved with Renoise 2.1?
If Renoise did not spit out an error while saving its very very unlikley that it saved the file “wrong”.
What does this “fast shutdown” exactly do? If it kills all applications&the system instead of properly shutting it off you should better avoid using it.
You can try to repair the song file with for example winrar or any other zi prepair tool. If you don’t know how, send it over to me and I’ll see what I can do to repair it…