Error while using DML to backup file storage

Question

Hello,

I am seeing an exception in below call. This works most of the time but throws an exception randomly.

                   await TransferManager.CopyDirectoryAsync(
                    sourceFileDir: sourceDirectory,
                    destFileDir: destinationDirectory,
                    isServiceCopy: true,
                    options:copyDirectoryOptions,
                    context:transferContext,
                    cancellationToken:cancellationTokenSource.Token);

Exception:

"Failed to validate destination."

"   at Microsoft.WindowsAzure.Storage.DataMovement.DirectoryTransfer.<ExecuteAsync>d__1b.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at Microsoft.WindowsAzure.Storage.DataMovement.TransferManager.<DoTransfer>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n   at DmlExec.Functions.<CopyDirectoryAsync>d__12.MoveNext() in C:\

Inner Exception:

{"The remote server returned an error: (405) Method Not Allowed."}

"   at Microsoft.WindowsAzure.Storage.Core.Executor.Executor.ExecuteSync[T](RESTCommand`1 cmd, IRetryPolicy policy, OperationContext operationContext) in c:\\Program Files (x86)\\Jenkins\\workspace\\release_dotnet_master\\Lib\\ClassLibraryCommon\\Core\\Executor\\Executor.cs:line 604\r\n   at Microsoft.WindowsAzure.Storage.File.CloudFileDirectory.Create(FileRequestOptions requestOptions, OperationContext operationContext) in c:\\Program Files (x86)\\Jenkins\\workspace\\release_dotnet_master\\Lib\\ClassLibraryCommon\\File\\CloudFileDirectory.cs:line 49\r\n   at Microsoft.WindowsAzure.Storage.File.CloudFileDirectory.CreateIfNotExists(FileRequestOptions requestOptions, OperationContext operationContext) in c:\\Program Files (x86)\\Jenkins\\workspace\\release_dotnet_master\\Lib\\ClassLibraryCommon\\File\\CloudFileDirectory.cs:line 176\r\n   at Microsoft.WindowsAzure.Storage.DataMovement.AzureFileDirectoryLocation.Validate()\r\n   at Microsoft.WindowsAzure.Storage.DataMovement.DirectoryTransfer.<ExecuteAsync>d__1b.MoveNext()"

Any idea what could be causing this error?

Thanks!