During Sync`s you may receive an error something like "sync-generic-failure" With no real information on what the error is. No issues seem to be seen, and is rather just cosmetic. But we don`t like errors right !!!
Fig 1 - AAD Connect Error
Possible CauseDuring the setup of AAD Connect, you may or may not have noticed the option for "Group Write-Back" (At the time of writing this is still in preview). However, even though this sounds cool, there are some pre-reqs that need to be adhered too. (i.e. Exchange 2013 cumulative update 8 or Later). So in this case the platform we saw was still only Exchange 2010 !. And a group was created on O365 and was trying to write-back to On-Prem.
REF: https://docs.microsoft.com/en-gb/azure/active-directory/connect/active-directory-aadconnect-feature-preview#group-writeback
Solution
Either Disable "Group Write-Back", Remove the Groups created directly in Office 365 or Install the version of Exchange stated above.
