[Bug Report] Sometimes SendEventAsync fails with UnauthorizedAccess

# Context

- **OS, version, SKU and CPU architecture used:** Windows 10 Desktop, Windows 11 Desktop
- **Application's .NET Target Framework: .NET 8
- **Device:** PC
- **SDK version used: 1.42.3

## Description of the issue
We are using the iot sdk to send events to an iot hub. We are using certificate based authentication. We are seeing a lot of intermittent `Unauthorized Access` errors. Here is a stack trace:
```
Microsoft.Azure.Devices.Client.Exceptions.UnauthorizedException: error(condition:amqp:unauthorized-access,description:{"errorCode":401002,"message":"Unauthorized access","trackingId":"086E25554C674B1782FB73BA73B6B752-G2:-TimeStamp:2025-07-01T12:59:54.653313718Z","timestampUtc":"2025-07-01T12:59:54.653313718Z","info":null})
---> Microsoft.Azure.Amqp.AmqpException: {"errorCode":401002,"message":"Unauthorized access","trackingId":"086E25554C674B1782FB73BA73B6B752-G2:-TimeStamp:2025-07-01T12:59:54.653313718Z","timestampUtc":"2025-07-01T12:59:54.653313718Z","info":null}
at Microsoft.Azure.Amqp.AsyncResult.End[TAsyncResult](IAsyncResult result)
at Microsoft.Azure.Amqp.AmqpObject.OpenAsyncResult.End(IAsyncResult result)
at Microsoft.Azure.Amqp.AmqpObject.EndOpen(IAsyncResult result)
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location ---
at Microsoft.Azure.Devices.Client.Transport.AmqpIot.AmqpIotSession.OpenSendingAmqpLinkAsync(IDeviceIdentity deviceIdentity, AmqpSession amqpSession, Nullable`1 senderSettleMode, Nullable`1 receiverSettleMode, String deviceTemplate, String moduleTemplate, String linkSuffix, String correlationId, CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at Microsoft.Azure.Devices.Client.Transport.AmqpIot.AmqpIotSession.OpenSendingAmqpLinkAsync(IDeviceIdentity deviceIdentity, AmqpSession amqpSession, Nullable`1 senderSettleMode, Nullable`1 receiverSettleMode, String deviceTemplate, String moduleTemplate, String linkSuffix, String correlationId, CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.AmqpIot.AmqpIotSession.OpenTelemetrySenderLinkAsync(IDeviceIdentity deviceIdentity, CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.AmqpIot.AmqpUnit.EnsureSessionIsOpenAsync(CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.AmqpIot.AmqpUnit.EnsureSessionIsOpenAsync(CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.AmqpIot.AmqpUnit.OpenAsync(CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.Amqp.AmqpTransportHandler.OpenAsync(CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.ProtocolRoutingDelegatingHandler.OpenAsync(CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.ErrorDelegatingHandler.<>c__DisplayClass27_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Microsoft.Azure.Devices.Client.Transport.ErrorDelegatingHandler.ExecuteWithErrorHandlingAsync[T](Func`1 asyncOperation)
at Microsoft.Azure.Devices.Client.Transport.RetryDelegatingHandler.OpenInternalAsync(Boolean withRetry, CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.RetryDelegatingHandler.EnsureOpenedAsync(Boolean withRetry, CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.RetryDelegatingHandler.<>c__DisplayClass22_0.<b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Microsoft.Azure.Devices.Client.TransientFaultHandling.RetryPolicy.<>c__DisplayClass34_0.<g__TaskWrapper|0>d.MoveNext()
--- End of stack trace from previous location ---
at Microsoft.Azure.Devices.Client.TransientFaultHandling.RetryPolicy.RunWithRetryAsync[T](Func`1 taskFunc, ShouldRetry shouldRetry, Func`2 isTransient, Action`3 onRetrying, Boolean fastFirstRetry, CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.TransientFaultHandling.RetryPolicy.RunWithRetryAsync(Func`1 taskFunc, ShouldRetry shouldRetry, Func`2 isTransient, Action`3 onRetrying, Boolean fastFirstRetry, CancellationToken cancellationToken)
at Microsoft.Azure.Devices.Client.Transport.RetryDelegatingHandler.SendEventAsync(Message message, CancellationToken cancellationToken)
```

On the IoT hub we see
```
ResourceType
IOTHUBS
OperationName
deviceConnect
ResultType
401002
ResultDescription
Unauthorized access
Level
Error
DurationMs
0
SourceSystem
Azure
connectionId_g
0171242d-8387-4402-bebb-d26cb41b8b38
RelatedActivityId_g
4efcfc26-de8a-4193-adf7-6515b23cc4eb
identity_s
LSUOKFFUWLPQ
properties_s
{"statusCode":"401","errorMessage":"Unauthorized access","deviceId":"LSUOKFFUWLPQ","trackingId":"1BD5E33A0CE848F68202D439E5252E5C-G2:-TimeStamp:2025-07-01T13:00:54.682360032Z","authType":null,"protocol":"Amqp","sdkVersion":".NET/1.42.3+2a97dd06e82cb67c5be8a7c7d189bef8048a3a86 (.NET 8.0.17; Microsoft Windows 10.0.19045 WindowsProduct:0x00000030; X64; {3C59FEBE-1D13-4709-84A3-B5A31FF22988})","maskedIpAddress":"146.185.0.XXX"}
location_s
WestEurope
Type
AzureDiagnostics
```
## Code sample exhibiting the issue

```
// in init code
var certWithPw = new X509Certificate2(certificate, "");
var auth = new DeviceAuthenticationWithX509Certificate(proxyId, certWithPw);
hubClient= DeviceClient.Create(hub, auth, TransportType.Amqp);

// we have our own retry mechanism, so we don't want to use build-in retry
hubClient.SetRetryPolicy(new NoRetry());
...
// in message handler (factory defined elsewhere)

using var hubMessage = MessageFactory.CreateMessage(rawData);
await hubClient.SendEventAsync(hubMessage, ct);
```

Start at AmqpIotSession.OpenSendingAmqpLinkAsync and AmqpUnit.EnsureSessionIsOpenAsync, following the SendEventAsync path through RetryDelegatingHandler. Reproduce the certificate-authenticated AMQP send and compare the client stack trace with the IoT Hub deviceConnect diagnostics. Done means the intermittent UnauthorizedAccess failure is explained and addressed, with SendEventAsync behaving reliably under the reported conditions.

Written by the indexing model from the issue text.