Redmi Note 9S!! WLAN ISSUE
Brice replied at 2020-04-23 02:34:01
When you let the device go to sleep for few hours or minutes wifi stops working. It does not lose the connetion to the wifi. It just has no more access to the internet and the device does not switch to mobile internet on it's own. You need to turn off the wifi and reconnect it again in order to gain internet access.
Same issue in both, 2,4ghz and 5ghz seperate networks or together in one SSID. Switching the wifi standards 802.11a/b/g/n/ac has also no effect. Likewise changeing the Private DNS option ore the use of a static IP in the network.
In the Mi Community are already some other threads regarding this big BUG:
Even at XDA it's a Topic:
https://forum.xda-developers.com ... ps-leaving-t4085213
A german android forum also trys to find the cause:
https://www.android-hilfe.de/for ... 6gb-128.944828.html
And even a german review is mentioning this BUG:
Most of the users have a FritzBox and they are very popular in germany. It's not an problem of the FritzBox because every other divice is working. Only the Note 9S has this problem.
The Note 9S is so far the only device available on the German/international market with a Qualcomm 720G, which makes the theory of a driver bug somehow likely. The realme 6 Pro, which also has it built in, is currently not available in markets where the Fritzbox is so strongly represented as in Germany and from this direction I haven't heard of any problems. Fritzbox is trying hard to keep all routers up to date with the latest software and the WiFi driver of the 720G might not work with certain new network standards or protocols.