The CA API gateway 9.4 (software version)product by default pushing all the API errors as the response header "x-ca-err". But if we considering the production support team who need to investigate the errors from the API gateway logs, they will have tough time without the respective API gateway errors not getting printed to the Audit log. We did follow-up this part with the support team and received a customized fix/patch via SQL script. At present we are trying to validating the custom fix on our environment.
It will be great if you can consider this fix in future release, production support team required ample support for their trouble shooting steps, also definitely they wont be having access to the Relying Party environment.
The support case for the reference: 20066156