sometimes I do not have data transfer through the normally connected wifi connection.
But my WiFi network is fine and working normal with other devices.
Nothing was changed here.
No new device or firmware update.
Only change in the whole network was the beta firmware on my S9+.
Only thing that fixes the problem temporary is either waiting some minutes or restarting the S9+.
Restarting the router or disable and then enable WiFi on the S9+ did not help.
My router is a AVM FritzBox 6490 Firmware 7.12
I am about 3-5m away with direct sight.
Also it does not make a difference, if 2.4Ghz and 5GHz have the same or a different SSID.
I am always connected with 5GHz.