please test the following: setup a WiFi network with parallel 2,4ghz and 5ghz WiFi channels with the same SSID.
Normally the device and the router talk with each other and the device gets the best network (2 or 5 GHz).
I think the Nokia tries too hard to change the network so i have situation where the phone shows me I have perfect WiFi connection but that is not correct. I have to disable WiFi and then enable it again. Or I wait like 60 seconds until the phone itself reconnects or drops WiFi and takes the LTE network. This is very annoying!
Every other device and my old smartphone did that without any problem. Please check this scenario. Thanks in advance.