JSON keys must be strings. If the source data is a map that uses structures as keys, the Data Integration Service serializes the keys when you export the data. The exported JSON file might include escape characters before double quotation marks that are added during serialization.
JSON does not support binary data. When you export data that includes binary keys, the Data Integration Service replaces the key with the string "<binary>" which results in invalid JSON.
If the source data is a map that contains duplicate keys of a complex data type, the Data Integration Service might produce invalid JSON when you export the preview data.