After i updated to ios 8.4 and itunes 12.2.. And synced my ipad and iphone... all my playlists got messed up.. most got deleted and iPad and iPhone showed different playlist... Total mess.... re-syncing just jumbled things around and still left the mess .
After many trials and errors the followng workd for me:
1- Back up all devices in iTunes to the computer .. Not icloud ( for safety reasons)
2- Turn on "iCloud music liberary" in itunes 12.2 preferences/general .. ( default is off.. but on on ios.. This may be one sourse if the problem )
Wait for iCloud library sync to complete.
3- Sync your devices, if things get messed .. Its ok .
4- Go to your device Settings on iphone or ipad... , settings/music and turn off iCloud music library .
Dont panic.. Playlists and some some or all songs will disappear. ( on iPad all songs disappeared , on iPhone only playlists)
5- Turn "iCloud music library" back on . Wait for library to load .
At this point all playlists and songs should reappear and nothing should be missing
6 - Try resyncing to make sure all is smooth and clear.
also.. If u have problem with streaming songs added to playlists not showing try the following:
For streaming songs to show up in playlists once they are added ... Go to playlist tab on your device. Click on the "my/all/apple playlist PINK link" to show the drop down menu
From the menu turn off "music available offline( only show music on device)" option.. Turn it off.. No green .
All of the above worked on my ipad and iphone.. Both of which got screwed up after ios 8.4 , itunes 12.2 followed by sync through itunes.
Apple... All of the above should be transparent to the user.. The correct settings should be default.
And the process should clearly guid the user .