DKIM Failure Notices but Verification Works

About every 2-3 weeks, I receive e-mails and notifications at the top of my Dashboard that my DKIM validation isn’t working. And every time I go to the E-mail Authentication page to check, the DKIM validation is working fine. Since this is a key component to what we do, I need to know why this is happening and if my DKIM setup is indeed ok.