Haproxy doesn't forward request?

During NeutronSecGroupPlugin.create_and_delete_secgroups rally scenario we have found the following error:
from rally.log: http://paste.openstack.org/show/478326/
from haproxy: http://paste.openstack.org/show/478327/
The following request mathed with the time: http://paste.openstack.org/show/478328/
Can't see the request on neutron-server side: http://paste.openstack.org/show/478335/

Is it possible that haproxy didn't forward the request to neutron-server?
There was big load on the node with external vip (node-97): http://paste.openstack.org/show/478336/

Cluster Configuration:
Baremetal,Ubuntu,IBP,HA,Neutron-vlan,DVR,Ceph-all,Nova-debug,Nova-quotas,7.0-301-mu1
Controllers:3 Computes:178 Copmutes+Ceph:20 LMA:2

api: '1.0'
astute_sha: 6c5b73f93e24cc781c809db9159927655ced5012
auth_required: true
build_id: '301'
build_number: '301'
feature_groups:
- mirantis
fuel-agent_sha: 50e90af6e3d560e9085ff71d2950cfbcca91af67
fuel-library_sha: 5d50055aeca1dd0dc53b43825dc4c8f7780be9dd
fuel-nailgun-agent_sha: d7027952870a35db8dc52f185bb1158cdd3d1ebd
fuel-ostf_sha: 2cd967dccd66cfc3a0abd6af9f31e5b4d150a11c
fuelmain_sha: a65d453215edb0284a2e4761be7a156bb5627677
nailgun_sha: 4162b0c15adb425b37608c787944d1983f543aa8
openstack_version: 2015.1.0-7.0
production: docker
python-fuelclient_sha: 486bde57cda1badb68f915f66c61b544108606f3
release: '7.0'

Diagnostic Snapshot: http://mos-scale-share.mirantis.com/fuel-snapshot-2015-11-09_14-09-50.tar.xz