REST API Link/PowerShell/UpdateProvisioningTask fails with error ""

Using swagger I see the following error when I call the Link/PowerShell/UpdateProvisioningTask function:

The full response body is:

{
"Message": "An error has occurred.",
"ExceptionMessage": "Index was out of range. Must be non-negative and less than the size of the collection.\r\nParameter name: index",
"ExceptionType": "System.ArgumentOutOfRangeException",
"StackTrace": " at System.ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)\r\n at System.Collections.Generic.List`1.set_Item(Int32 index, T value)\r\n at Unify.Product.Plus.LinkEngine.<>c__DisplayClass92_0.<UpdateProvisioningTask>b__0()\r\n at Unify.Product.Plus.LinkEngine.<>c__DisplayClass161_0.<ConfigurationChange>b__0()\r\n at Unify.Framework.ExtensionMethods.WaitOnMutex(Mutex mutex, Action work)\r\n at Unify.Product.Plus.LinkEngine.UpdateProvisioningTask(Guid linkId, Boolean incoming, ProvisioningStep step, IProvisioningTaskInformation taskInformation)\r\n at Unify.Product.Plus.LinkEngineAuditingDecorator.UpdateProvisioningTask(Guid linkId, Boolean incoming, ProvisioningStep step, IProvisioningTaskInformation taskInformation)\r\n at Unify.Product.Plus.LinkEngineNotifierDecorator.<>c__DisplayClass50_0.<UpdateProvisioningTask>b__0()\r\n at Unify.Framework.Notification.NotifierDecoratorBase.Notify(ITaskNotificationFactory notificationFactory, Action action)\r\n at Unify.Product.Plus.LinkControllerBase.InnerUpdateProvisioningTask[TExtended](Guid linkId, Boolean incoming, ProvisioningStep step, Guid taskId, IProvisioningTaskApiInformation`1 taskInformation, XElement extended)\r\n at Unify.Product.Plus.LinkController.UpdatePowerShellProvisioningTask(Guid linkId, Boolean incoming, ProvisioningStep step, Guid taskId, PowerShellProvisioningTaskApiInformation taskInformation)\r\n at lambda_method(Closure , Object , Object[] )\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClassc.<GetExecutor>b__6(Object instance, Object[] methodParameters)\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()"
}

I will attach my configuration extensibility files to the next comment.