Hello, I have a 2016 MBP 2.6/1tb/460. I have an iTunes library of about 200 gigs. I've just come from Lion in my iMac, where everything runs buttery smooth in iTunes, exact same collection. Now in Sierra 10.12.1, iTunes V184.108.40.206, almost every second click causes a beachball! Sometimes it runs OK for 30 mins, but inevitably it starts freaking out. Is this a known issue? Is there a cure? Thanks!