LEDE 17 to OpenWRT 19.07.03 - WiFi unstable after upgrade - STA-OPMODE-SMPS-MODE-CHANGED

Hello there,
I just upgraded my perfectly working TP-Link TL-WDR4900 v1 from LEDE 17 to the latest OpenWRT firmware available.

Unfortunately now, some WiFi 2.4GHz clients got stuck on wifi, they cannot even ping the router, the only way to fix it is to manually disconnect and reconnect their WiFi.

This is the log from the router:

May 30 22:26:01 Router hostapd: wlan1: STA-OPMODE-SMPS-MODE-CHANGED 83:20:75:40:f3:a0 static
May 30 22:26:11 Router hostapd: wlan1: STA-OPMODE-SMPS-MODE-CHANGED 83:20:75:40:f3:a0 dynamic
May 30 22:38:59 Router hostapd: wlan1: STA-OPMODE-SMPS-MODE-CHANGED 83:20:75:40:f3:a0 static
May 30 22:38:59 Router hostapd: wlan1: STA-OPMODE-SMPS-MODE-CHANGED 83:20:75:40:f3:a0 dynamic
May 30 22:39:03 Router hostapd: wlan1: STA-OPMODE-SMPS-MODE-CHANGED 83:20:75:40:f3:a0 static
May 30 22:39:04 Router hostapd: wlan1: STA-OPMODE-SMPS-MODE-CHANGED 83:20:75:40:f3:a0 dynamic
May 30 22:39:12 Router hostapd: wlan1: STA-OPMODE-SMPS-MODE-CHANGED 83:20:75:40:f3:a0 static
May 30 22:39:13 Router hostapd: wlan1: STA-OPMODE-SMPS-MODE-CHANGED 83:20:75:40:f3:a0 dynamic

What is this about?
Cheers

Fabio

@fcecamor, welcome to the community!

Did you keep the settings?

Hii, thanks.

No, I started from zero, setting all as new.