Just got a late 2015 iMac i7 and find that iMovie is constant crashing on me. Lots of beach balls and then it closes down... I previously had a late 2013 iMac i5 and it did the same thing. I thought the new iMac with more power would eliminate the beach balls and crashes. I'm not doing anything I'd consider to be very intensive. Just home videos etc. Is iMovie just known to be twitchy or is there something else I'm doing wrong?