I've never heard of that b4 & not sure why you have that problem. It sounds to me like you've moved the files from their original location from the time your created the playlist. That's the problem with playlists. They point to the location of the files/songs that they were at the time the playlist was created. So if you move them later the player won't be able to find them.

The file being in red is what makes me think this might be the case here. remember a playlist is simply a file that lists the titles & points to the location of the file. A playlist doesn't contain any music itself. It's simply a reference file.