I bought this router to replace an ISP basic one, notably for better PS5 gaming. Where this has largeely worked, yesterday I had a poor connection. I use a Wifi snooper on my mobile and I'm getting very confused by the results and why the signal strengths can vary so much.

The router and PS5 are fixed in place, the router directly below 2m through a wooden floor, both near a window. During the evening, signal strength was going up and down 10 dBm or more. Why?? What's interfering with the signal when there's nothing physical changing between the source and receiver?

Furthermore, I had the Wifi power set to High and was getting about -55 dBm strength. I changed it to Medium and the wifi signal went up a bit to -52 dBm. I've just this second changed it to High and signal strength has improved a bit. When I first installed the Router and set power to high, I was getting much stronger than -40 dBm, but now it's not managing to get that output despite nothing changing. Just changed it to Low and strength dropped to -58 and then changed back to high and now it's -45, whereas before High was -52.

How come the signal strength changes so radically?