Didn't know this before but are Apple lossless or AAC m4a files compatible with 3rd party apps? I've been getting a lot of DRM type messages where the song can't be played or streamed errors on my iOS devices.
I believe what you are seeing is that the software sees a familiar extension however when it opens the file it doesn't contain data that it can decode, thus throwing an (incorrect) error. If you created these files on your computer, they should not have any DRM under any circumstance anyway.