My iPhone 6 and my iMac running Yosemite synch fine together. And I have the SMS forwarding on so non-iMessage texts go to my iMac. All is good. But my MacBook running Mountain Lion acts very weird. It takes forever to synch, and when it does, some threads are missing messages. Some of the threads are totally out of order. Text from last night appearing after text from this morning. Doesn't make any sense. And my MacBook does not get any of the SMS texts. Maybe I can't forward SMS to more than one mac? Is this why it's not synching on the MacBook perfectly? Or does it have something to do with the iMac running a newer OS? Can anyone shed some light on this? I blocked all content on my Flash Player as suggested by another thread from 2013, but it's not fixing anything.