magnum2000 replied at 2020-07-02 22:50:58
I have opened a ticket, then they told me to wait the 1.0.3 firmware.
Then, I have upgraded the firmware and this problem no longer appears.
Now, I have replaced the phone because it continuously crashed, and with the new one, always seller by Amazon in Italy, the firmware is stocked at version 1.0.1, so I have problem again with the WiFi.

Hello,

I have a RN9Pro too, 11.0.4.0 version. A workaround was implemented and whenever group key timeout occours in sleep mode it is detected and the device reconnects to AP, sending a new DHCP request. It is acceptable as a workaround, I hope it will be fixed properly in MIUI12.