So as a way around this error message, we created a brand new certificate with all 73 SANs in original certificate that was stuck with this error message. The certificate validated and was issued very quickly, no CAA record issues or any other issues. I then went back to the problem certificate. I cancelled the pending order, then the auto renewal process started since it is one day away from expiration. I then got a correct error message the one of the SANs had a problem with the CAA record. I removed this SAN, then it automatically resubmits. Now I have the error message "2021-01-27 19:14 GMT Let’s Encrypt: Error finalizing order :: Rechecking CAA for \ (backslash)". This is no longer an urgent matter, but we do want to know if this is a bug or not, and if the only way around it is to create a new certificate entirely like we did.