sync with imatch / icloud

DjayPro user for a few years. A lot of problems to sync 16000songs with itunes from pc to ipad. (itunes 11, IOS 8.1.2).Everytime I have to reboot the Ipad. Then songs disappeared on ipad, after a time (hours&hours…) songs appear in grey. Download 16000 songs from de Itunes library doesn’t work. Imatch is ON / Icloud is On. What do I wrong ?