Wifi on RPI 4 8GB

I have just received my RPI4 8GB version, and I am having problems connecting to my home wifi. I have 2 RPI3s which have no problem connecting. Is this a common problem or is there a fault with my RPI4.

I have a 4b 4 gig and 4B 8 gig, both work OK on my 2.4 GHz WIFI. 5 GHz is a bit iffy but I put that up to where my router is located. It works on 5 GHz but I get occasional drops. Might also be the metal heatsink case my 8 gig is in.
Did you set you correct country / Location in raspi-config?
What type of case, if any are you using?
Did you try 2.4 and 5 GHz?
What exactly happens or doesn’t happen?

Wasn’t there a problem some time ago where the WiFi would not work when certain (high, 4k) screen resolutions were being used or did that get resolved?

@cucola are you using regular full-HD or some other screen resolution?

It’s enclosed in a Pilbow case and 5gh. It take ages to connect to wifi and when using vnc very frequently loses connection only to reconnect at an indeterminate time later.
This doesn’t happen with my RPI3s. The monitor is lower than 4k, but it’s an old monitor with dvi to hdmi converter cable.

I’d give the 2.4 GHz band a try, just to see how it works.