The below NPE is seen in [1]

Also teardown failed:
New exceptions found: 3
[{'warnerr_list': [168, 185, 232, 244, 245], 'lines': [u'2018-07-03T16:09:48,093 | ERROR | org.opendaylight.yang.gen.v1.urn.opendaylight.netvirt.natservice.rev160111.napt.switches.RouterToNaptSwitch_AsyncDataTreeChangeListenerBase-DataTreeChangeHandler-0 | AsyncDataTreeChangeListenerBase | 256 - org.opendaylight.genius.mdsalutil-api - 0.5.0.SNAPSHOT | Thread terminated due to uncaught exception: org.opendaylight.yang.gen.v1.urn.opendaylight.netvirt.natservice.rev160111.napt.switches.RouterToNaptSwitch_AsyncDataTreeChangeListenerBase-DataTreeChangeHandler-0', u'java.lang.NullPointerException: null', u'\tat org.opendaylight.netvirt.natservice.internal.AbstractSnatService.removeLearntIpPorts(AbstractSnatService.java:470) [350:org.opendaylight.netvirt.natservice-impl:0.7.0.SNAPSHOT]', u'\tat org.opendaylight.netvirt.natservice.internal.AbstractSnatService.handleSnatAllSwitch(AbstractSnatService.java:152) [350:org.opendaylight.netvirt.natservice-impl:0.7.0.SNAPSHOT]', u'\tat org.opendaylight.netvirt.natservice.internal.FlatVlanConntrackBasedSnatService.handleSnatAllSwitch(FlatVlanConntrackBasedSnatService.java:48) [350:org.opendaylight.netvirt.natservice-impl:0.7.0.SNAPSHOT]', u'\tat org.opendaylight.netvirt.natservice.internal.SnatServiceManagerImpl.notify(SnatServiceManagerImpl.java:61) [350:org.opendaylight.netvirt.natservice-impl:0.7.0.SNAPSHOT]', u'\tat org.opendaylight.netvirt.natservi

[1]https://jenkins.opendaylight.org/releng/view/netvirt/job/netvirt-csit-1node-openstack-pike-tempest-stateful-snat-conntrack-fluorine/5