I have been having this problem since early 2015 and on 4 different phones so far.
Apple have only suggested a 'Restore from New' which didn't solve the problem.
I'm still dealing with this problem every day.
[doublepost=1481111392][/doublepost]It's been happening to me for the past 2 years and still catches me out every day. It happens on new phones, restored phones and my iPad. No help from Apple.
The problem is if I decide to leave Apple Music all my music disappears.
15 years of collecting digital music.
Gone.