Internal Server Error when trying to list the Protected Items via the REST API

Hello,

I cannot get the "Protected Items" REST API (List) to work. It is documented this way:
"Provides a pageable list of all items in a subscription, that can be protected."

I keep getting an Internal Server Error (code 500).

I believe I have read the documentation properly (https://docs.microsoft.com/en-us/rest/api/recoveryservices/protecteditems). Most of my other calls (like "backupJobs") work so I know I am able to make the Azure Backup REST API work.

The URL I'm using is (GET) : https://management.azure.com/subscriptions/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/resourcegroups/LdrResourceGroup/providers/Microsoft.RecoveryServices/vaults/LdrVault/backupProtectedItems?api-version=2016-08-10

I have obfuscated the subscription id for security reason. I have tried with a different api version (2016-06-01) and Subscription with a upper case "S", so as to exactly mimic the documentation but the result is the same:

Response status code : 500
Response status phrase : Internal Server Error
Response text :
===============
{
    "error": {
        "code": "CloudInternalError",
        "message": "Microsoft Azure Backup encountered an internal error.\r\nWait for a few minutes and then try the operation again. If the issue persists, please contact Microsoft Support.",
        "target": null,
        "details": null,
        "innerError": null
    }
}

How can I get the list of protected items via the REST API?

Thanks in advance,

Laurent.