Apple Music app import functionality add the music files but they are all only 10s long.
I import a bunch of m4a files from a local disk and they all end up being 10s long. I can see the file sizes do not imply 10s. I'd say this started a couple of weeks ago and I cannot find any way to resolve this. I do have over 500k songs in my music library but I believe the maximum is 1M.
MacBook Pro 17″, macOS 10.13