When any of the mandatory field is empty, task fails.
In the XSD, if any field referred as base that means mandatory, hence the parser fails if the empty values is passed.
Please modify the XSD from the SOAP provider end to make the field as optional or pass value.
Let us know if this helps.
This is a generic error which is seen for UDT transformations .
If you are using this first time please check if required packages are enabled for your org or not.
Please check if you are reading the source as File or Data? That may cause the issue sometimes.