Congratulations on your discovery. I think using OSX to create homebrew Playlist files is the main problem. I do not hold SanDisk responsible for a quirk of OSX. Here is a link to a similar discussion and the same solution in the SanDisk Forum way back in 2017.
“CRLF line endings required in Playlist m3u files”
http://forums.sandisk.com/t/random-problem-in-playlists/68672/12
