Doorbell showing poor wifi even with the Extender next to it

I've setup my new Ring Doorbell 2 and it looks like it's working ok other than it's showing as having a poor WiFi. When I start Live view, or try to speak to someone it's very slow to load and the voice is breaking up. I've tried moving the wifi extender pretty much right next to the doorbell but it still shows weak wifi on the device health / dashboard. Anything else I can try? Edit: with a WiFi analyser I get approx -48 RSSI value right next to the doorbell, so there's a good enough signal, but the doorbell does not work properly.