CloudSearch domain returns Error (AmazonCloudSearchDomainException)

Hi, Some of our search domain don't work any longer and just show "Error" in the dashboard for "Searchable Documents". When we query documents we just get the following exception: Amazon.CloudSearchDomain.AmazonCloudSearchDomainException: The service returned an error with Error Code InternalError and HTTP Body: {"__type":"#InternalError","error":{"message":"[Deprecated: Use the outer message field] "},"message":""} [11:34:30 ERR ::1 00-3881ffae54f07deba569cd907fc35d40-74525c3ff55107d8-00] An unhandled exception has occurred, The service returned an error with Error Code InternalError and HTTP Body: {"__type":"#InternalError","error":{"message":"[Deprecated: Use the outer message field] "},"message":""} at Amazon.Runtime.Internal.Unmarshaller.InvokeAsync[T](IExecutionContext executionContext) at Amazon.Runtime.Internal.HttpErrorResponseExceptionHandler.HandleExceptionStream Please help to resolve this or explain how we can avoid this in the future. Any ideas?