Microsoft Graph通知不稳定

Question

我们已订阅Microsoft Graph通知来更改用户资源

var result = await _client.Subscriptions.Request().AddAsync(new Subscription() {
        ChangeType = "updated,deleted",
        NotificationUrl = /* skipped */,
        ExpirationDateTime = DateTimeOffset.UtcNow.AddDays(1),
        Resource = "/users",
    }, token);

也用于用户其他资源的更改

var result = await _client.Subscriptions.Request().AddAsync(new Subscription() {
        ChangeType = "updated,deleted",
        NotificationUrl = /* skipped */,
        ExpirationDateTime = DateTimeOffset.UtcNow.AddDays(1),
        Resource = "/Users/{email}/{resource}",
    }, token);

我们每天都将通知更新为新通知。 现在我们已经观察到来自Microsoft Graph API的通知有时会来，有时却不会。

是什么原因导致此类不稳定的通知？