vnet jails loose network connectivity

Hello all, i use jails for some testing, but i can not seem to make it 
stable.
I use vnet jails with a bridge but when i put some load on it, some 
jails loose there network connectivity.

My setup is as follows, haproxy internal IP 10.233.185.20 using binat to 
make it Public accessable.
Then a varnish jail, and two web servers al on the 10.233.185.x range.

If i give it a little load with hey (hey -h2 -n 10 -c 20 -z 60s 
https://wp.test.nl) than within the test the haproxy jail is not 
reachable anymore it is not pingable from the host machine, and from the 
other jails. restarting the jails solves it, if i leave the system alone 
for some time i saw the varnish jail become unresponsive.

If i do a tcpdump on the epair${name}a interface i do see the packages 
from the host machine to the jail but the jail itself is not reachable.

There is nothing in the logs from the host and the jail itself, i can 
ping the jails ip adres from the jail itself.


I do not think i have a special setup, but i could be doing something wrong.
my jail.conf

# Global settings applied to all jails.
$domain = "test.nl";
$subdomain = "";

exec.start = "/bin/sh /etc/rc";
exec.stop = "/bin/sh /etc/rc.shutdown";
exec.clean;

mount.fstab = "/storage/jails/$name.fstab";

exec.system_user  = "root";
exec.jail_user    = "root";
mount.devfs;
sysvshm="new";
sysvsem="new";
allow.raw_sockets;
allow.set_hostname = 0;
allow.sysvipc;
enforce_statfs = "2";
devfs_ruleset     = "11";

path = "/storage/jails/${name}";
host.hostname = "${name}${subdomain}.${domain}";

# Networking
$uplinkdev        = "vtnet1";
$epid             = "${ip}";
$subnet           = "10.233.185.";
$cidr             = "/24";
$ipv4_addr        = "${subnet}${ip}${cidr}";
vnet;
vnet.interface    = "vnet0";

$epair=epair${ip};
vnet;
#vnet.interface    = "${epair}b";  # default vnet interface
exec.prestart     = "ifconfig bridge0 > /dev/null 2>&1 || ( ifconfig 
bridge0 create up && ifconfig bridge0 addm $uplinkdev )";
exec.prestart    += "ifconfig ${epair} create up description 
jail_${name}   || echo 'Skipped creating epair (exists?)'";
exec.prestart    += "ifconfig bridge0 addm ${epair}a           || echo 
'Skipped adding bridge member (already member?)'";
exec.created      = "ifconfig ${epair}b name vnet0";
exec.start        = "/bin/sh /etc/rc";
exec.consolelog   = "/var/log/jail/$name.test.nl";
exec.stop         = "/bin/sh /etc/rc.shutdown";
exec.poststop     = "ifconfig bridge0 deletem ${epair}a";
exec.poststop    += "ifconfig ${epair}a destroy";

varnish01 {
     $ip = 16;
     mount.fstab = "";
     path = "/storage/jails/${name}";
}

web01 {
     $ip = 18;
}

web02 {
     $ip = 19;
}

haproxy {
     $ip = 20;
     mount.fstab = "";
     path = "/storage/jails/${name}";
}

My ifconfig

bridge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 
1500
     ether 58:9c:fc:10:ff:82
     inet 10.233.185.1 netmask 0xffffff00 broadcast 10.233.185.255
     id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15
     maxage 20 holdcnt 6 proto rstp maxaddr 2000 timeout 1200
     root id 00:00:00:00:00:00 priority 32768 ifcost 0 port 0
     member: epair20a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
             ifmaxaddr 0 port 13 priority 128 path cost 2000
     member: epair19a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
             ifmaxaddr 0 port 53 priority 128 path cost 2000
     member: epair18a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
             ifmaxaddr 0 port 48 priority 128 path cost 2000
     member: epair16a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
             ifmaxaddr 0 port 28 priority 128 path cost 2000
     groups: bridge
     nd6 options=9<PERFORMNUD,IFDISABLED>
epair16a: flags=8963<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> 
metric 0 mtu 1500
     description: jail_varnish01
     options=8<VLAN_MTU>
     ether 02:76:32:8e:0e:0a
     groups: epair
     media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
     status: active
     nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
epair18a: flags=8963<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> 
metric 0 mtu 1500
     description: jail_web01
     options=8<VLAN_MTU>
     ether 02:6d:be:b8:36:0a
     groups: epair
     media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
     status: active
     nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
epair19a: flags=8963<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> 
metric 0 mtu 1500
     description: jail_web02
     options=8<VLAN_MTU>
     ether 02:54:fd:77:9a:0a
     groups: epair
     media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
     status: active
     nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
epair20a: flags=8963<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> 
metric 0 mtu 1500
     description: jail_haproxy
     options=8<VLAN_MTU>
     ether 02:f8:58:06:78:0a
     groups: epair
     media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
     status: active
     nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>

This is on both 13-STABLE and 14-HEAD.