I have 2 OS X machines (a Macbook & iMac), an iPad, and 2 iPhones. My photos, keychains, bookmarks, iCloud drive, etc. do sync reliably & predictably, though t

I have 2 OS X machines (a Macbook & iMac), an iPad, and 2 iPhones. My photos, keychains, bookmarks, iCloud drive, etc. do sync reliably & predictably, though the iOS devices need to be on WiFi to sync their photos. The only area I've had some problems lately with are Contacts. I'll update a contact in one space and not see it updated on another device consistently. Not sure why.