Please also see comment https://bugs.launchpad.net/neutron/+bug/1760047/comments/24 - it may be that patch https://review.openstack.org/626830 is triggering this issue now more often.
Please also see comment https:/ /bugs.launchpad .net/neutron/ +bug/1760047/ comments/ 24 - it may be that patch https:/ /review. openstack. org/626830 is triggering this issue now more often.