It never hurts to fix the tags, but they shouldn’t matter that much to a playlist. As I understand it, a playlist is a list of songs and locations in order—first this song in this folder, then that song in that folder, etc. I don’t understand about what the OP said about sometimes song, sometimes album, etc., but the playlist—not the track numbers in this case–should determine the order IF the playlist is working correctly.
Try changing the type of playlist WMP is making–look through the settings, and if you’re using. m3u change to pla or vice versa.
Or try another music software, like Media Monkey, which also makes playlists.
