Yep I agree. It does sound like a placement issue. @Begbie have you popped the zyxel air app on your phone and connected to the WiFi on the router. It'll give you signal stats so useful for finding a suitable spot. FYI it can take a few seconds for the app to update when moving the router.
So I've done this (three app) and I can get a 5g signal, but fairly poor but as the 4g signal is stronger it will still continually switch over.
My phone is consistently receiving 5g, with good speeds.
I've asked to return it as no matter how good a signal I can achieve it will continuously switch over to 4g eventually. Which is a shame as when it's working I'm getting 400meg.
I might try getting the v2, as it might even be something physically wrong with the router after some searching.