Dreadful wi-fi on hAP lite (10% ping loss, average latency 600 ms)

We have a bunch of hAP lite (RB941-2nD) routers. Each serves as a gateway for 1-5 devices total. Usually it’s an IP camera connected by cable and a laptop connected by wifi.

ROS 6.34.8 (latest).

[admin@MikroTik] > /interface wireless print detail 
Flags: X - disabled, R - running 
 0  R name="wlan1" mtu=1500 l2mtu=1600 mac-address=CC:2D:E0:61:EA:73 arp=enabled 
      interface-type=Atheros AR9300 mode=ap-bridge ssid="WD642" frequency=auto band=2ghz-g/n 
      channel-width=20/40mhz-XX secondary-channel="" scan-list=default wireless-protocol=802.11 vlan-mode=no-tag 
      vlan-id=1 wds-mode=disabled wds-default-bridge=none wds-ignore-ssid=no bridge-mode=enabled 
      default-authentication=yes default-forwarding=yes default-ap-tx-limit=0 default-client-tx-limit=0 
      hide-ssid=no security-profile=wlan_security_profile_main compression=no

/interface wireless spectral-history screenshot is attached to this message.

Laptop is placed in 2-3 meters away from hAP lite. In given config, we have no loss, ping latency min 1ms, max 800ms, average 100 ms.

Tried to change channel-width to 20mhz (should’ve create less interference), and ping loss went to 10%, average latency 600 ms. Pinging the hAP lite, of course.

Is there something we can do to make hAP lite provide stable wifi for 1 laptop? Also tried to ping hAP lite from a tablet, same thing. Please help to fix this.
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