For input string: "null"
An unknown internal error has occurred. Ninety percent of the time this is usually the result of an invalid value being entered within the <AudioChannelMapping> tag.
Ensure that your manifest file validates in the XML Manifest Validator in Backlot. Review all entries and make sure all the information listed accurately reflects the information provided in the Source Request and the values used are valid. You can use an XML editor such as Oxygen to validate the manifest against the our metadata XSD. This will highlight any unsupported values.