RetryOptions error-handler in Orchestration cannot capture right exception-type from Sub-Orchestration

My question is related to [436](https://github.com/Azure/durabletask/issues/436) and [807](https://github.com/Azure/durabletask/issues/807)- this is explained below:

**Problem**:
Cannot get the right exception (via InnerException or FailureDetails) in the exception handler of RetryOptions (Handle)

**Scenario**:
I have an Orchestration that calls a sub-orchestration using RetryOptions, like:

```
RetryOptions retryOptions = new RetryOptions(TimeSpan.FromMilliseconds(2500),3){
Handle = e =>
{
/*
This exception never captures MyCustomException, which was originally thrown,
either in FailureDetails or the InnerException property
*/

SubOrchestrationFailedException tfe = e as SubOrchestrationFailedException;

if (tfe != null && tfe.InnerException != null)
{
e = tfe.InnerException;
}

MyCustomException ce = e as MyCustomException;
if (ce != null)
{
LatestException = ce; //LatestException is a variable of type MyCustomException
return true;
}
return false;
}};
// IPayload is a custom type that is supposed to be returned from my sub-orchestration(if it ran successfully)
return await context.CreateSubOrchestrationInstanceWithRetry(typeof(FetchRatesSubOrchestration), retryOptions, 1);
```

The sub-orchestration's RunTask() looks like:

```
public override async Task RunTask(OrchestrationContext context, object input)
{
List rates = new List();
Reference1 reference1 = await context.ScheduleTask(typeof(TaskActivity1));
await context.ScheduleTask(typeof(TaskActivity2), reference1);
rates = await context.ScheduleTask>(typeof(TaskActivity3), reference1);
List datasReceived = rates.Select(x => x.TickerName).ToList();
List validDataPoints = _dbContext.SourceKeys.Select(t => t.SourceKeyValue).ToList();
List missingDataPoints = datasReceived.Except(validDataPoints).ToList();
if (missingDataPoints.Count() > 0)
{
_logger.LogError($"Requested data points {string.Join(",", missingDataPoints)} were not returned in the response. Retrying.");
throw new MyCustomException($"Requested data points {string.Join(",", missingDataPoints)} were not returned in the response. Retrying.");

//OrchestrationFailureException innerExceptionToThrow = new OrchestrationFailureException($"Requested data points {string.Join(",", missingDataPoints)} were not returned in the response. Retrying.");
//throw innerExceptionToThrow;
// var exc = new DurableTask.Core.Exceptions.SubOrchestrationFailedException($"Orchestration failed - {GetType().Name}", innerExceptionToThrow);
// exc.FailureDetails
// throw exc;
}
return new RatesAvailablePayload(rates);
}
```

The error thrown within the if-block in the sub-orchestration never bubbles-up to the Handle error-handler of the defined RetryOptions (within the parent orchestration).

**Additionally, what else have I tried?**
**a**. Setting the ErrorPropagationMode to ErrorPropagationMode.UseFailureDetails (or ErrorPropagationMode.SerializeExceptions) doesn't help - the FailureDetails object of the exception and the InnerException property are always null.

**b**. I have tried debugging against the source of the framework, and, I believe to have seen the "_Multiple ExecutionCompletedEvent found, potential corruption in state storage_" message from the SerMarkerEvents() method in DurableTask.Core.OrchestrationRuntimeState class - but that was during one of the times I was debugging it.

**c**. While debugging the framework source, I noticed that the FailureDetails object is populated, for the most part, but due to the parallel-execution of the code it is a little difficult to debug as the control jumps from one class to the other, and then to the third - which makes following a trail difficult, at best

**d**. I have looked at most, if not all, of the tests in the [DurableTask](https://github.com/Azure/durabletask.git) and the [DurableTask-MSSQL](https://github.com/microsoft/durabletask-mssql.git) repositories, but these haven't helped me in figuring out what I may still be missing

I'm using the following packages:

**Microsoft.DurableTask.SqlServer** - 1.1.1
**Microsoft.Azure.DurableTask.Core** - 2.10.0 (dependency brought in via Microsoft.DurableTask.SqlServer)

Please advise on how to get this resolved.

Thank you.