I found a work around, but still doesn't solve how to stop the problem happening.
After syncronise if i drag the left page from my A-master spread back onto my B-master page then it makes it based on it again and fixes it.
But i would still love to know how to stop it from happening otherwise this will waste a lot of time.
Please provide us with much more information:
- With which version do you work?
- Is the other document you work with saved in the same version?
- When it comes from an older version, was it saved as IDML in the new version? Opened and saved again as INDD?
1) Working on InDesign CC
2) Yep both created from scratch in the same version
3) Nope didn't come from an old version