If the script aborts with below error, then it is the issue with configuration of l2_encap attribute under sth::traffic_config.
{log {can't read "userArgsArray(vlan_id)": no such element in array}} {status 0}
Possible reason for this error: The configuration includes VLANs but l2_encap is set to -l2_encap ethernet_ii
RESOLUTION:
If we have VLAN in our configuration, then l2_encap attribute has to be set to -l2_encap ethernet_ii_vlan to resolve the issue.