Yes, that is an issue I have and currently I have not found a resolution.  I have tried to update it with query from the sys_watermark table but as of yet I have not been successful.  The behavior is less than optimal but doesn't affect the approvals.  We determined it was acceptable and our users preferred to have these in one email rather than our approvers getting multiple emails.  I have not had any issues with this behavior.  When I have a resolution I will be sure to post it.