I get this error message EVERY time I try to play a game on my 2nd console.
I understand that this issue generally pops up when Xbox 1 has not finished uploading your cloud save data before you start trying to play the same game on Xbox 2. However, I get this message EVERY time.
For instance, on Xbox 1 I played Shadows of Mordor, then I had Xbox1 on for another ~10 hours without loading up that game again (which should be plenty of time to upload the latest save data for Shadows of Mordor). Yet, when I log on to Xbox 2 I still get the error that the other Xbox is taking too long to sync. It's almost as if Xbox1 isn't uploading my cloud data at all (it is connected to Xbox Live).