Cannot update oauth2PermissionGrants using graph.microsoft.com - microsoft-graph-api

Question

Using https://graph.microsoft.com/beta/oauth2PermissionGrants I now cannot use POST to update B2C apps to grant them access to API's due to an error : Missing property: expiryTime
We've been using the BETA endpoint to update our B2C apps to grant them access to various API's using a Powershell script I created however in the last week or so something has changed on the back end as we now receive an error when attempting a POST : Missing property: expiryTime. The expirytime however is present in the JSON.
We can POST via graph.windows.net using the same JSON so this is something specific to the BETA endpoint. When querying the App's Oauth2permissiongrants I also cannot see the expirytime or starttime using graph.microsoft.com for some reason.
Please see the code below and let me know if I can answer any questions.
https://developer.microsoft.com/en-us/graph/graph-explorer#
POST https://graph.microsoft.com/beta/oauth2PermissionGrants
{
"clientId": "APP servicePrincial ObjectID",
"consentType": "AllPrincipals",
"expiryTime": "2030-05-12T19:34:28.9831598Z",
"principalId": null,
"resourceId": "02bccee7-8958-4e5e-89c7-466a5370a205",
"scope": "user_impersonation"
}
{
"error": {
"code": "Request_BadRequest",
"message": "Missing property: expiryTime",
"innerError": {
"request-id": "b15edafa-1415-4430-9d89-5ea3fb824f9c",
"date": "2019-09-16T11:29:39"
}
}
}