Wifi connectivity issues, possible Windows 10 security related

I have recently (1 or 2 months) been having issues with my WiFi connectivity. It frequently stops, and when I reconnect, I"m told that the Wifi 5G networks isn’t secure. I can reconnect, but it will often drop out again. If I switch to the slower wireless network, it seems to do ok.

I use Centurylink and have a fairly new Lenovo laptop. The security setup for the wireless router is WPA2-AES, which I understand to be an up to date security protocol.

Is there a flaw in the Windows 10 security system, the Century Link router, or even the wireless adapter in my computer?

Thanks,

Tom