@CWTK 

This is definitely bug. It is present in both Deco M5 and Deco M9 Plus. I reported it about 2 years ago, when I noticed it. Some people say, it does not manifest itself when Deco mesh runs in Router (default) mode. I run my Deco mesh in Access Point mode and I have not tested that claim. How do you run your Deco mesh: in Router or in AP mode?

It is unlikely TP-Link will fix that issue. It seems to be in third-party code they use in their Deco, and for newer models they either went with different third-party code or with different supplier. In many newer Deco models "Test Internet Speed" is just not present in Deco app, because Deco firmware does not support it.

My recommendation: just ignore it. This is just reporting issue, not real bandwidth throttling.

  @Alexandre. 
Yes I run it in AP mode too. Never tried it in router mode.

It is indeed not a big issue and can be ignored. Too bad they will not fix it.

  @Riley_S 

Hi,

I believe we are discussing "Test Internet Speed" button in Deco app, not Deco labs speed test.

  @Alexandre. Yes the deco app "Speedtest button". It looks like download result is half or limited to around 500. Since wired or wireless results on devices itself are higher than Deco app result shows.