Error 500 when trying to query getActivitiesByInterval route of Microsoft Graph - microsoft-graph-api

Question

I successfully retrieved a Microsoft Graph token with clientCredentials, but when I try to query the getActivitiesByInterval route (for a SharePoint site) I am receiving an HTTP 500 :
"code": "generalException",
"message": "The remote server returned an error: (500) Internal Server Error."
The application I registered has the following rights (Application) on Microsoft Graph (Files.Read.All, Files.ReadWrite.All, Sites.Read.All, Sites.ReadWrite.All, User.Read.All).
If I do exactly the same query with a token retrieved from graph explorer I received an HTTP 200 with the content I ask for.
The token I am using seems correct as I can retrieve the users on the Microsoft Graph without having an HTTP 500.
The code I am using to do the request is the following (it's an Azure Function with a Microsoft Graph binding to get the token):
[FunctionName("SharepointSitesViews")]
public static async Task Run([TimerTrigger("0 */5 * * * *", RunOnStartup = true)]TimerInfo myTimer,
[Token(Identity = TokenIdentityMode.ClientCredentials, IdentityProvider ="AAD", Resource = "https://graph.microsoft.com")] string graphToken,
ILogger log)
{
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", graphToken);
var response = await client.GetAsync("https://graph.microsoft.com/beta/sites/****MySiteId*****/getActivitiesByInterval?startDateTime=2018-09-12T09:59:19.817Z&endDateTime=2018-12-11T00:00:00.000Z&interval=day");
var me = await response.Content.ReadAsStringAsync();
}
The same code with the url "https://graph.microsoft.com/v1.0/users" returns a 200.
I have also reproduce the same 500 error using postman :
GET /beta/sites/****MySiteId****/getActivitiesByInterval?startDateTime=2018-09-12T09:59:19.817Z& endDateTime=2018-12-11T00:00:00.000Z& interval=day HTTP/1.1
Host: graph.microsoft.com
Authorization: Bearer *****myToken****
cache-control: no-cache