Just to add, it seems to have been fine with a strong signal at the start. I only noticed the signal strength go down after I updated the firmware to 1.5.3 Build 20210203 Rel. 68223. I've attempted to reset the router but to no luck. Any chance of a firmware fix coming soon?

@prinsipengharry 

I have Deco M5 with same firmware version as yours. At the distance of 8 feet signal strength on my smartphone connected to M5 is reported as Excellent. That's on 5GHz, with 2.4GHz turned off. To be more technical, signal strength is -45 dBm according to WiFi Analyzer app on that same smartphone.

I measured the distance and, just like you, tested signal strength on smartphone with Deco M5 in clear sign.  

Either you've got defective unit, or you have too much WiFi interference from your neighbours. Have you tried "Network Optimization" in Deco app? If, after first run, on every run it tells your Deco WiFi network still needs optimizing, that would be a bad sign.

@Alexandre. 

Hi,

Yeah, I figured there was no way the signal strength could be this bad. I did try optimizing, and I think that made it worse to be honest. I've already set up an appointment with my ISP to return to their store.

Thank you, this further convinces me I've got a defective device.