I'm experiencing the same issue as described here:
Summary: Every hour, we have a large amount of users being created only to be deleted the following hour, and so on. These users have all been deleted from AD and removed from the associated AD group.
As suggested by Ann Worley (see link above), we disabled incremental synchronisation and the issue above is no longer occurring but how can we revert back to incremental synchronisation again without this reoccurring?