hAP ac2 very high latency in client mode with Fritzbox

Hi,
I try to work with my hAp ac2 in client mode connected to Fritzbox AP router.
Wifi of mikrotik is dhcp client, fritzbox is dhcp server

After scan and connection with the fritzbox I can ping the fritzbox with ping rates around 2 ms via winbox but only if I’m directly connected with the ethernet port of my notebook to ethernet port of mikrotik. I use here a different subnet than dhcp of my fritzbox. Ports of mikrotik are not bridged.

If I try to connect to the mikrotik over wifi via my fritzbox (same subnet), I can barely use winbox, and ping rates go up to 1 sec.

Also a simultaneous ping with my notebook to the fritzbox gets ping spikes to 500 - 900 ms

I dont understand why my wifi connection gets so bad during a winbox connection to my mikrotik router and as soon as I disconnect it gets better.
Also Paketsniffer shows a lot of TCP retransmissions as soon as I use winbox.

name=“wlan1” mtu=1500 l2mtu=1600 mac-address=00-00-00-00-00 arp=enabled
disable-running-check=no interface-type=IPQ4019 radio-name=“XXXXXXXXX”
mode=station ssid=“XXXXXXXX” area=“”
frequency-mode=regulatory-domain country=germany installation=any
antenna-gain=3 frequency=2427 band=2ghz-b/g/n channel-width=20mhz
secondary-channel=“” scan-list=default wireless-protocol=802.11
rate-set=default supported-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps
supported-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps
basic-rates-b=1Mbps basic-rates-a/g=6Mbps max-station-count=2007
distance=dynamic tx-power-mode=default vlan-mode=no-tag vlan-id=1
wds-mode=disabled wds-default-bridge=none wds-default-cost=100
wds-cost-range=50-150 wds-ignore-ssid=no update-stats-interval=disabled
bridge-mode=enabled default-authentication=yes default-forwarding=yes
default-ap-tx-limit=0 default-client-tx-limit=0 wmm-support=disabled
hide-ssid=no security-profile=SecWifi wps-mode=push-button
station-roaming=disabled disconnect-timeout=3s on-fail-retry-time=100ms
preamble-mode=both compression=no allow-sharedkey=no
station-bridge-clone-mac=00:00:00:00:00:00 ampdu-priorities=0
guard-interval=any
ht-supported-mcs=mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7,mcs-8,mcs-
9,mcs-10,mcs-11,mcs-12,mcs-13,mcs-14,mcs-15,mcs-16,mcs-17,mcs-
18,mcs-19,mcs-20,mcs-21,mcs-22,mcs-23
ht-basic-mcs=mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7
tx-chains=0,1 rx-chains=0,1 amsdu-limit=8192 amsdu-threshold=8192
tdma-period-size=2 nv2-queue-count=2 nv2-qos=default nv2-cell-radius=30
nv2-security=disabled nv2-preshared-key=“” nv2-mode=dynamic-downlink
nv2-downlink-ratio=50 nv2-sync-secret=“” hw-retries=7 frame-lifetime=0
adaptive-noise-immunity=ap-and-client-mode
hw-fragmentation-threshold=disabled hw-protection-mode=none
hw-protection-threshold=0 frequency-offset=0 rate-selection=advanced
multicast-helper=default multicast-buffering=enabled
keepalive-frames=enabled

So I got it working.

Problem was my fritzbox AP had a problem with my 802.11n configuration on my mikrotik in client mode.

I switched to 802.11b/g on mikrotik, now it is working.

Strange thing is my dell notebook and android smartphone are working both in 802.11n configuration with that fritzbox…