Yes it's not a rights issue & probably does does have something to do with Apples Software. This might be a way to push there online music service ... IDK. Although music limits space, playing directly off my phones storage is okay for me. It saves me data, & paying for a music service. So this isn't going to suddenly make *me* want to pay for a music service.
Question for those of you posting recently, have you been facing this problem since April of 2016, or is it just new for you. This the so called *solution* to this problem.
"Tracks on an older playlist may have been edited (possibly only the meta data or lyrics text) to a new version on Apple Music, thereby invalidating the old version. You can delete the old track from the list and add the new version from Search to update your playlist.
Tracks that were once available, may have been retracted by the artist or their record company, temporarily or permanently, for all regions or for selected regions. The availability of tracks can change over time. "
About the 2nd part of this answer, that's why I absolutely hate listening to music on my phone nowadays. I listen to some fairly obscure music, and it's not all on iCloud. A great line from the Movie High Fidelity sums it up. when Rob Gordon says “I get by because of the people who make a special effort to shop here, mostly young men, who spend all their time looking for deleted Smith singles and original, not rereleased underlined Frank Zappa's albums. Fetish properties are not unlike porn. I'd feel guilty taking their money, if I wasn't... well... kinda one of them.” Still I don't play any obscure tracks on my phone. I already know they won't play.
The first part of the answer did solve the problem for me though. It isn't worded very clear though. Apple did edit a large chunk of my music library (80 plus %). I simply connected my phone, went into iTunes, deselected every album that had previously worked, and synched. This deleted every song from my phone. I then reselected my music, and viola, problem was solved.
Still since the problem occurred after an update, why hasn't Apple figured out a way to fix this data problem, in the 3 years since.