PostgreSQL Major Version Upgrade Issues

We have an issue upgrading Azure Database for PostgreSQL flexible server from version 14 to version 18.

We have followed the Major version upgrades in Azure Database for PostgreSQL guide.

The upgrade was attempted on a restored backup instance as suggested by the guide. The main issue is the lack of information on why the upgrade is failing.

The failure has a status of Conflict - An unexpected error occured while processing the request. Tracking ID: '9d955699-4f3a-405f-a9fa-2d1ba9f883fb' (Code: InternalServerError).

The operation details only show the following:

{
    "status": "Failed",
    "error": {
        "code": "InternalServerError",
        "message": "An unexpected error occured while processing the request. Tracking ID: '9d955699-4f3a-405f-a9fa-2d1ba9f883fb'"
    }
}

Getting more insights about why the upgrade fails is crucial. Please advise on how to continue and what additional information you need in order to identify and resolve the issue.