Ansible Automation Platform 2.5 installer fails with Bad API request: 503 Server Error: Bad Gateway for url

Issue

• Ansible Automation Platform 2.5 installer fails with :

  fatal: [controller.example.com -> gateway.example.com]: FAILED! => {"attempts": 10, "changed": false, "cmd": ["aap-gateway-manage", "migrate_service_data", "--username", "admin", "--merge-organizations", "true", "--api-slug", "controller"], "delta": "0:00:06.827993", "end": "2025-08-15 12:35:18.250641", "msg": "non-zero return code", "rc": 1, "start": "2025-08-15 12:35:11.422648", "stderr": "2025-08-15 12:35:16,827 INFO      ansible_base.lib.redis.client Removing setting cluster_error_retry_attempts from connection settings because its invalid for standalone mode\n2025-08-15 12:35:16,906 INFO      ansible_base.resources_api.rest_client Making get request to https://gateway.example.com:443/api/controller/v2/service-index/metadata/.\nCommandError: Bad API request: 503 Server Error: Service Unavailable for url: https://gateway.example.com:443/api/controller/v2/service-index/metadata/", "stderr_lines": ["2025-08-15 12:35:16,827 INFO      ansible_base.lib.redis.client Removing setting cluster_error_retry_attempts from connection settings because its invalid for standalone mode", "2025-08-15 12:35:16,906 INFO      ansible_base.resources_api.rest_client Making get request to https://gateway.example.com:443/api/controller/v2/service-index/metadata/.", "CommandError: Bad API request: 503 Server Error: Service Unavailable for url: https://gateway.example.com:443/api/controller/v2/service-index/metadata/"], "stdout": "Starting migration\nGetting service metadata", "stdout_lines": ["Starting migration", "Getting service metadata"]}