@jruyssen I have exactly the same issue.

i have a deco m5 network connected to a router provided by my broadband provider (Gigaclear) via a network switch.

the switch allows me to connect certain other devices directly to the broadband router.

the broadband router is able to connect to the internet at 580mbps pretty much always (I am paying for 600, so not bad)

anything connected directly to the switch gets approximately the same speed.

until 14/4/24 my deco network would test at about 330mbps continuously- sometimes a touch slower, sometimes a bit faster, but always about that and had been like that for about a year

after 14/4/24 every test is producing 95mbps plus or minus 1.

two questions:

1) why could the deco network not reach 600mbps in the first place? I understand that speeds are halved for wireless connections, but mine is wired....

2) what on earth happened at around 14/4 to mean that it can no longer negotiate speeds?

I am using v1.7.6 build 20240305 rel 38320

does it have a bug?
 

  @jruyssen SLOW SPEEDS ARE DUE TO LATEST FIRMWARE UPDATE: ROLL BACK TO FIX!

I have 600Mb/s broadband fibre coming into my house and achieve that on a PC connected directly to it. My deco network hangs off the broadband router. I used to achieve between 350-400 Mbs. On 14/5 my network speed dropped to 100mbs and stuck there. i get a warning message about the cable on the WAN port. Chnaged the cable today. no change, still 100mbs. 

Then i realised: my firmware was updated on 14/5 to v1.7.6. 

Today i rolled back the firmware to v1.7.4

Guess what? 400 Mbs again.

Conclusion: there is a bug in 1.7.6 and you need to go back to an older firmare to get gigabit speeds.....

to do this:

- log into your deco via a webbrowser within your deco network

- choose firmware update

- hit browse

- download v1.7.4 from tplink (google: Download for Deco M5 then under firmware)

- select and hit install on your webbrowser

- system will reboot, and when it comes back so will your speed!

note: this CANNOT be done from the DECO App. It must be from a webbrowser. Also, it must the the website within your DECO network. You cannot roll back from outside of it.

I hope this helps you guys!