I have exactly the same sort of problem. I have .m4a files in iTunes that I wanted to compare with .wav files. I can't convert the iTunes .m4a back into .wav.
I can use Switch to convert .wav to .m4a and then back into .wav. What's special about .m4a files created by iTunes ??
They didn't even originate from a CD ripping process - they are LPaudio tracks converted to .wav by Audacity and then transferred into .m4a by iTunes so that I can hear them on my Sonos.
