Connection to 5 GHz radio unstable

Installing and Using OpenWrt
1

I have very unstable connection to 5 GHz radio after upgrade to 21.02.3 (openwrt-21.02.3-ramips-mt7620-) and when the client device is brought to adjoining room. Simple web browsing is not possible as webpages seem to load an eternity and client gets ultimately disconnected.
The system log shows repetitive patterns like:

Mon Jun  6 08:15:22 2022 daemon.notice hostapd: wlan0: STA-OPMODE-N_SS-CHANGED fa:b8:0e:89:c6:4d 1
Mon Jun  6 08:15:22 2022 daemon.info hostapd: wlan0: STA fa:b8:0e:89:c6:4d IEEE 802.11: associated (aid 3)
Mon Jun  6 08:15:22 2022 daemon.notice hostapd: wlan0: AP-STA-CONNECTED fa:b8:0e:89:c6:4d
Mon Jun  6 08:15:22 2022 daemon.info hostapd: wlan0: STA fa:b8:0e:89:c6:4d WPA: pairwise key handshake completed (RSN)
Mon Jun  6 08:26:13 2022 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED fa:b8:0e:89:c6:4d

Mon Jun  6 08:27:01 2022 daemon.notice hostapd: wlan0: STA-OPMODE-N_SS-CHANGED fa:b8:0e:89:c6:4d 1
Mon Jun  6 08:27:01 2022 daemon.info hostapd: wlan0: STA fa:b8:0e:89:c6:4d IEEE 802.11: associated (aid 3)
Mon Jun  6 08:27:01 2022 daemon.notice hostapd: wlan0: AP-STA-CONNECTED fa:b8:0e:89:c6:4d
Mon Jun  6 08:27:01 2022 daemon.info hostapd: wlan0: STA fa:b8:0e:89:c6:9d WPA: pairwise key handshake completed (RSN)
Mon Jun  6 08:35:32 2022 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED fa:b8:0e:89:c6:4d

Can anyone tell me what kind of event is STA-OPMODE-N_SS-CHANGED ?
What is OPMODE-N_SS ?
Also what is the meaning of the number after the client MAC at the end of respective line (which is 1 in the examples above) ?
How could I identify why do I have this problem?

2

https://patchwork.kernel.org/project/linux-wireless/patch/1516173508-16528-1-git-send-email-tamizhr@codeaurora.org/

3

@lleachii Thank you for the hint. Now I know that N_SS stands for number of spatial streams. But do you know what is the purpose of the message telling that the number of spatial streams has changed?
Anyway, it does not seem to be very informative. Neither as to why connection to 5 GHz radio is so bad , nor as to why the client gets disconnected ultimately :frowning: