The default values of the properties of the 'org.openecomp.resource.vl.extVL' exported are incorrect.
For example:
The 'type' of 'network_role' property is 'string', but its default '{}' is a object, not a string.

node_types:
  org.openecomp.resource.vl.extVL:
    derived_from: tosca.nodes.Root
    description: ECOMP generic virtual link (network) base type for all other service-level and global networks
    properties:
      network_role:
        type: string
        default: {}

The complete template file of 'org.openecomp.resource.vl.extVL' exported from SDC:

resource-Extvl-template.yml