Hello. I've been having this issue since last fall and can't find any resolution. I've called into Apple support several times and have been working with a Senior Advisor. I've provided Apple with access to my Mac and my iPhone and sent them debugging info and videos of me reproducing the issue multiple times (about an hour process on the phone with Apple each time). Their engineers haven't reported any updates. I've seemed to isolate the issue to songs that I previously matched with iTunes Match before subscribing to Apple Music. This came to light because of the Favourites playlist automatically generated by Apple Music every week. I set it to download and every week, the playlist would download, until the fall (sometime around iOS 11.0). Now, only songs from Apple Music successfully download and songs that were from my library from years ago have an infinite loop, and the playlist is in a constant state of downloading. I can also reproduce this with similar songs directly from my library. The odd part is that I can listen to them by streaming. I just can't download them for offline listening. New music from Apple Music downloads just fine. Another odd part is that this only affected my iPhone and iPad up until this month, and now my Mac is experiencing the same issue. Has anyone experienced this or have any suggestions? Thanks so much!