Cannot upload large attachment by upload session simultaneously

[datanglibai]

Describe the bug I'm using Micosoft.Graph 4.11.0 to send email with attachment, but in recent days I always get below error when more than 2 files upload simultaneously. it is reproduced every time.

Status Code: PreconditionFailed\r\nMicrosoft.Graph.ServiceException: Code: ErrorIrresolvableConflict\r\nMessage: The send or update operation could not be performed because the change key passed in the request does not match the current change key for the item.\r\n\r\n at Microsoft.Graph.SimpleHttpProvider.<SendAsync>d__10.MoveNext()

To Reproduce Steps to reproduce the behavior: Code of mine private async Task attachFiles() { foreach (var largeFile in largeFiles) { tasks.Add(UploadLargeFile(message, largeFile)); } await Task.WhenAll(tasks); }

private async Task UploadLargeFile(Message message, CustomerFile largeFile, int index) {

        var attachmentItem = new AttachmentItem
        {
            AttachmentType = AttachmentType.File,
            Name = largeFile.Name,
            Size = largeFile.Content.Length,
        };

        UploadSession uploadSession = await EmailGraphClient.Users[account].Messages[message.Id].Attachments
            .CreateUploadSession(attachmentItem)
            .Request().PostAsync();
        using (System.IO.MemoryStream ms = new System.IO.MemoryStream(largeFile.Content))
        {
            var largeFileUpload = new LargeFileUploadTask<byte[]>(uploadSession, ms);                
            await largeFileUpload.UploadAsync();
        }
    }

Expected behavior No exception

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Desktop (please complete the following information):

• OS: windows 10
• .net framework 461
• Micosoft.Graph 4.11.0

Additional context Add any other context about the problem here.