Hi Martin,
1. As far as I know, windows 10 1607 CBB hasn't been release, and your windows 10 1511 is CBB, if you want to upgrade to 1607, you need to change it to CB mode;
2. Please check if the SCCM\WSUS has installed KB3159706 before syncing 1607;
3. If the above suggestions still couldn't resolve your issue, you'd turn to SCCM forum for more professional help:
https://social.technet.microsoft.com/Forums/en-US/home?forum=configmanagersecurity
Best Regards,
Anne
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