Do not sync with a computer when using match!

i Just wanted to warn people in case it happens to them and/or find out if others see similar. I use match/iCloud music library on my iPhone 6 Plus. and although that negates the need to sync with iTunes I still do it. Maybe to sync occasional movies as it's faster than cloud wifi downloads and also to just check sync is still working. But annoyingly if I do a sync then it seems to duplicate a number of songs in my music app. Even though they are locally stored I get another version showing with no album art. They seem to be linked as if I manually delete these dupes from the device the original listing no longer plays despite the store symbol unless I 'remove download' and then make it available offline. Well it does actually play but it streams in. So basically doing a sync with iTunes causes issues, if iCloud music library is switched on it should not touch the music app when I sync surely. as long as I never sync then the app is fine and a perfect mirror of my iTunes music library. But this is a real annoyance