@Brian2001 This is what I finally did to fix this.
First I renamed my 2.4G SSID to NAME2, keeping the 5G as NAME.
Then I created a file in /boot using
sudo nano /boot/wpa_supplicant.conf
In that file I put:
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=[your country code - 2 letters, caps, mine is NL for Netherlands]
network={
ssid="your 5G SSID"
psk="your wifi password"
key_mgmt=WPA-PSK
}
Then save the file and reboot. Remember the quote marks for ssid (wifi name) and psk (password).