TCP Connection Reset by Peer using CORS settings with Access

I enabled Access to protect our self hosted CRM (subdomain) using a rule to allow users ending in

I then set a CORS rule to allow the main website lead form to submit data to the CRM.
(Curl, silent post.)

Allow-Control-Allow-Origin = domain name of main site.
Access-Control-Allow-Methods = Allow All Methods
Access-Control-Allow-Headers = Allow All Headers

After applying this, it takes much longer for the data to submit, and returns the success page, but a warning is appearing, "TCP Connection Reset by Peer."

I then deleted these rules and made a new policy for the IP of the server to BYPASS and it worked as expected.

Does anyone have an answer for this behavior?