I've had the same problem for about 92 songs out of 4700 or so. One even says I purchased it in 2014. Most I think are songs from CDs. Been playing with, and been frustrated with, after turning on lossless, and Apple replacing songs with HLS audio, and no longer in my library, but moved into Apple Music folder. One cannot do anything with the song except listen to it. Good for those who just listen. I use LogicPro to Loop portions of songs I want to learn in the difficult bars, and have these areas loop over and over. Makes it much easier. You cannot move or do anything with HLS media. These are located in iTunes Media, but not in the music folder. This is something that should've been made very clear. However, it appears you can delete the download by clicking after selecting all of the HLS audio files listed by putting them together clicking on. Must do a command and make sure that kind is checked off and shows up. Then in preferences turn lossless off, after selecting ACC 256 kbps, then re-downloading and they get replaced with ACC 256 kbps files, mostly, and moved back to the music folder. However, there are some that are difficult to switch out and a source of frustration. This is something that should've been made clear before turning on lossless and sync, with iTunes match or Apple Music subscription. I've got rid of almost all of the HLS songs, then backed up with Carbon Copy Cloner to a separate SSD drive. I now have numerous folders of my library containing the entire Music folder of my library in different states. I have everything pretty much under control except for those 92 songs, "Waiting...". Please advise if you find a solution.
I've heard people say to log out and log back in, but don't say what to log out of. I'm assuming your Apple ID in iTunes or iCloud? This can be problematic sometimes. One person said it worked for them to get rid of the "Waiting...". I've also found that just quitting the music app, and opening the Music app again fixes some things that were apparently "stuck" in some iCloud status. Best, Seth