Payment form option for username check availablity not working correctly.

After upgrading to the most recent CiviCRM release our payment forms for membership sign up will no longer allow users to use the "Check Availability" option when attempting to select a username. Continually receive the message "Error checking username. Please reload the form and try again."

All CiviCRM extenions are up to date and all Wordpress plugins are up to date. Nothing really shows in our error logs in relation to this issue and at a loss for next steps. Any help/guidance would be appreciated.

CiviCRM 5.38.0 / WordPress 5.7.2