I'm running iOS9 on an iPhone 6 and OS X 10.10 Yosemite. Yesterday I shut my computer down in the early evening, and then used my phone for all texting that night and this morning. When I turned on my computer and checked iMessage this morning, only some of my texts were synced to the mac. One conversation took a few minutes to update, and others simply weren't updated to match the most recent texts at all. What causes this? I've signed out of iMessage on phone and mac (and signed back in) to "be sure," but how do I prevent this from happening? Is it inevitable?