A change to an attribute or new members are present on the group in meta DB but not the metaverse search in FIM.
In FIM the groups have this sync error:
Find the object in the metaverse and disconnect ALL connectors from the metaverse object.
Search the metadb connectorspace from the meta DB MA, search for the metadbguid of the object (You should get this from metadb SQL table).
Right click meta DB and select search connector space and you'll see the box below.
Run a preview on this, you will see it is successful. Then commit the preview.
Join the O365 object back to the metaverse object, you can do this by following this article:
Once done run a commit preview, you will see the NEW object is auto-deleted and the old object is joined.
Then do an export to 365 and confirm all is fixed by checking the group membership in the 365 portal.