Ring doorbell 2 poor wifi connection

I dont understand why my doorbell has poor wifi. The router is no more than 2m away buy the window, so no real blockages. I have external wireless CCTV cameras that are much further away and they work perfectly t Fine. The doorbell was fine for the 1st 2 weeks and then decided not to work properly. If someone rings the doorbell I would be likely if I get a chime, and if I do it is majorly delayed. I have rang support and they politely blame my wifi, which I know is not the problem as everything else including Nest works fine. Keep getting told to buy the extender, but why if the plug would in fact be further away than the router. Does anyone have any suggestions apart from bining it?