disappearing ping on bridge interface

Hi all.
I have a trouble with pinging (and accessing) some devices configured as bridge.
For example, I’m pinging both devices, and phone adapter behind second device, and ping response from first and/or second device disappearing sometimes, but I’m getting response from phone adapter at the same time (so I think this is not wireless or cable trouble).
There is a schematic diagram (clickable):

RB Groove 5Hn config:

[admin@xxx] /interface bridge> exp com
/interface wireless
set 0 basic-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps channel-width=10mhz \
    default-forwarding=no disabled=no frequency=5330 frequency-mode=\
    superchannel l2mtu=2290 mode=bridge \
    nv2-cell-radius=25 radio-name=xxx rate-set=configured scan-list=\
    default ssid=yyy supported-rates-a/g=\
    6Mbps,9Mbps,12Mbps,18Mbps,24Mbps tdma-period-size=10 tx-power=19 \
    tx-power-mode=all-rates-fixed wireless-protocol=nv2

/interface vlan
add interface=ether1 l2mtu=1594 name=vlan174-e vlan-id=174
add interface=wlan1 l2mtu=2286 name=vlan174-w vlan-id=174
add interface=ether1 l2mtu=1594 name=vlan400-e vlan-id=400
add interface=wlan1 l2mtu=2286 name=vlan400-w vlan-id=400

/ip address
add address=10.11.200.2/24 interface=bridge400

/ip route
add distance=1 gateway=10.11.200.1

/interface bridge
add l2mtu=1594 name=bridge174
add l2mtu=1594 name=bridge400

/interface bridge port
add bridge=bridge174 interface=vlan174-w
add bridge=bridge174 interface=vlan174-e
add bridge=bridge400 interface=vlan400-e
add bridge=bridge400 interface=vlan400-w

RB433AH has two wireless card - one of them configured as access point, another - as PtP link, and one VoIP adapter connected to ether1 port:

/interface bridge
add l2mtu=1526 name=bridge1

/interface wireless
set 0 band=2ghz-b/g basic-rates-a/g=\
    6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps basic-rates-b=\
    1Mbps,2Mbps,5.5Mbps,11Mbps channel-width=10mhz default-forwarding=no \
    disabled=no frequency=2417 frequency-mode=superchannel l2mtu=2290 mode=\
    ap-bridge name=wlan174-xxx radio-name=xxx scan-list=2300-2500 ssid=\
    xxx wireless-protocol=nstreme
set 1 basic-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps \
    basic-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps channel-width=10mhz disabled=no \
    frequency=5320 frequency-mode=superchannel l2mtu=2290 mode=station-bridge \
    name=wlan-ptp radio-name=yyyy rate-set=configured scan-list=\
    5100-5700 ssid=yyy tx-power-mode=all-rates-fixed wireless-protocol=\
    nv2-nstreme-802.11

/interface vlan
add interface=wlan-ptp l2mtu=2286 name=vlan174-w vlan-id=174
add interface=wlan-ptp l2mtu=2286 name=vlan400-w vlan-id=400

/interface bridge port
add bridge=bridge1 interface=ether1
add bridge=bridge1 interface=vlan174-w
add bridge=bridge1 interface=wlan174-yyy
/ip address
add address=10.11.200.3/24 interface=vlan400-w
/ip route
add distance=1 gateway=10.11.200.1

Problem appears when using nv2 protocol (and disappears with nstreme). For some reasons, I can’t use nstreme or 802.11 for this link.

Thanks

PS: Sorry for my english.