Getting lock exception when receiving messages from Service Bus in Service bus trigger Azure Function

Question

I prepared this code for receiving messages from service bus queue and sending email via SendGrid.

MessageLockDuration for my message on queue is set to 5 minutes and there is no other receiver except this function but still I am receiving the Error: An unhandled exception occurred in the message batch receive loop. Microsoft.Azure.ServiceBus: The lock supplied is invalid. Either the lock expired, or the message has already been removed from the queue, or was received by a different receiver instance. I am not sure what's wrong. Can you help?

public async Task Run([ServiceBusTrigger("%QueueName%", Connection = "ConnectionString")]Message[] messages, MessageReceiver messageReceiver, ILogger log,
             [SendGrid(ApiKey = "SendGridAPIKey")] IAsyncCollector<SendGridMessage> messageCollector)
        {
            log.LogInformation($"C# ServiceBus queue trigger function processed message: {messages}");
            try
            {
                BlobServiceClient blobServiceClient = new BlobServiceClient(StorageAccountConnectionString);
                BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(ContainerName);
                foreach (Message message in messages)
                {
                    CustomerRequest customerRequest = JsonConvert.DeserializeObject<CustomerRequest>(Encoding.UTF8.GetString(message.Body));
                    var msg = new SendGridMessage();
                    var memoryStream = new MemoryStream();

                    if (customerRequest.Type == TypeEnum.Today)
                    {
                        BlobClient blobClient = containerClient.GetBlobClient(customerRequest.FirstFileName);
                        var response = await blobClient.DownloadAsync();
                        await response.Value.Content.CopyToAsync(memoryStream);
                        foreach (var recipient in customerRequest.RecipientsDaily)
                        {
                            msg.AddTo(recipient);
                            msg.AddContent("text/html", "See Attached");
                            msg.SetFrom(new EmailAddress(SendGridSenderAddress));
                            msg.SetSubject("Subject");
                            var attachment = new Attachment
                            {
                                Filename = customerRequest.FirstFileName,
                                Content = Convert.ToBase64String(memoryStream.ToArray())
                            };
                            msg.AddAttachment(attachment);

                            await messageCollector.AddAsync(msg);
                        }
                    }
                    else
                    {
                        BlobClient blobClient = containerClient.GetBlobClient(customerRequest.SecondFileName);
                        var response = await blobClient.DownloadAsync();
                        await response.Value.Content.CopyToAsync(memoryStream);
                        foreach (var recipient in customerRequest.Recipients)
                        {
                            msg.AddTo(recipient);
                            msg.AddContent("text/html", "See Attached");
                            msg.SetFrom(new EmailAddress(SendGridSenderAddress));
                            msg.SetSubject("Subject");
                            var attachment = new Attachment
                            {
                                Filename = customerRequest.SecondFileName,
                                Content = Convert.ToBase64String(memoryStream.ToArray())
                            };
                            msg.AddAttachment(attachment);
                            await messageCollector.AddAsync(msg);
                        }
                    }
                    await messageReceiver.CompleteAsync(message.SystemProperties.LockToken);
                }
            }
            catch(Exception ex)
            {
                log.LogError($"Error occurred while processing the request {ex}");
            }
        }

        #endregion
    }