Recent iTunes song downloads not playing

I have recently downloaded numerous songs and albums from iTunes to Apple Music.

These recent downloads are (seemingly arbitrarily) becoming non-functional.

I download the song or album, and it plays on Music as expected.

Then, at some point in the relatively near future, it stops working.

• It's visible in Music
• The file is present in the hard drive folder with other functioning songs
• Trying to play the song does not work - as in clicking the "Play" arrow has no effect
• If these songs are synced to my iPhone 6S, they fail to play and a "Cannot open media damaged" error appears.
• This has not happened to any music burned from discs as far as I can tell (substantial sample size)
• I am pretty sure it is only affecting music downloaded through iTunes in the past month or so
• I can delete the music and re-download it, and it will work for a while, but then the issue reoccurs, repeatedly
• I have run "first aid" through the disc utility on the external drive that is hosting all of the music, and it is functioning fine, no issues

I have paid a substantial amount of money to Apple to download this music, and it is not playing properly.

I am also attempting to maintain an Apple Music subscription in case Apple is requiring that to continue to license ongoing use for paid downloads, but that has no effect. (If this is the case I will only buy CDs and burn them going forward! That seems like an exploitive business model.)

Does anyone have any advice as to how I can resolve this issue?

Thank you-