SmartPlaylist synced from Mac is empty on iPhone
My iTunes library is stored on my Macbook Pro. I have dozens of Smart Playlists. Before I started using Apple Music on my iPhone 6, all my songs & playlists sync'd from my Mac perfectly. Ever since enabling Apple Music on the iPhone, I've had nothing but problems syncing my own music. I am not using iTunes Match, btw.
Recently I found a post that suggested turning off Apple Music, then syncing music from the Mac, then re-enabling Apple Music, but selecting the 'merge' option, to merge the contents of both libraries. This worked initially, but eventually, all the smart playlists sync'd to my iPhone do not contain any songs. I don't have problems syncing my music to other Apple devices, but they don't have Apple Music enabled.
What am I doing wrong? This can't be how it's supposed to work.