SSO no longer functioning after upgrade to v13

After upgrading to v13.1.1, a specific SP-initiated SSO is no longer functioning. We receive the following errors:

 

Unable to find SAML SSO/SP Connector object matching SAML Authn Request

 

No SP Connector attached to sso (/partition/sitename-dev) matching authentication request. If ACS URL/Binding is present in authentication request it should match ACS URL/Binding from SP Connector. Issuer from the authentication request must match entity_id from SP Connector.

 

Unable to find SAML SSO/SP Connector object matching SAML Request

 

I confirmed via the SAML request that the Entity ID and ACS URLs are correct within the SP connector and that it is bound to the IdP service.

 

The very bizarre thing is that I was able to fix this by adding a SAML resource, webtop, and iRule to issue a 302 to the SAML resource. I don't understand why that would fix this.

 

Any info would be appreciated - thanks!