1.With wifi (at the moment) you will never reach the speed of 1000Mbps

2.The enviroment where your wifi is situated can change. A neighbour or even in your own surroundings like a new microwave or something like that can influence your wifi.

3.Yes the wifi of the router can degenerate and malfunction

A way to find the working modus of your connection is to wire up through a cable on the modem/router and do some tests as a start

Hi @ekaya, yalerta's already helped you with useful information, so I'll keep it short! 250 Mbit/s isn't that bad when you take into consideration that wifi is dependent on thousands of external factors which usually don't boost the speed, but temper it. 

Please take a look in our wifi troubleshoot: Hoe verbeter ik mijn wifi? | T-Mobile Community

Good luck and if you need help translating some of the tips, please feel free to ask or use Google Translate of course.

Hello @ekaya 

What about the cabled connection? Is it working fine?

Are you sure you are connected to 5 GHz and not 2,4 GHz?

Do you perhaps have another extender/router which causes problems?

@yalerta  I disagree with your comments as they are not helpful enough especially with point 1&2. Please read my initial entry before comment like this.

I didn't ask for 1000Mbps speed, my request was sharp drop since few days on my Wi-Fi speed quality after years. I am not a new user neither, so your inputs are ignored especially about my neighbors when I did analysis on channels/Wi-Fi health, thanks for your suggestions.

@Jason  thanks for your input.

Unfortunately, it is bad when you start receiving 250Mbps where you have been promised for more during your agreement with ISP. Again, I gave up expecting 1000 Mbps since last year, but 250 (¼ of promised upper bound limit of speed) is not acceptable from my side. It will lead T-Mobile losing client and I am surprised that I have been suggested to be happy with that. In this case there is no logic to use T-Mobile's advantages in terms of internet at home.

@Wag-cyclo  Thanks, I have tried both cable/ethernet and Wi-Fi with both types (2.4&5Ghz) and tested with different channel frequencies too with scanning surrounding channel frequency around my house.

In general, I opened this thread to understand what changed since last one week (it is still persists) that lead lack of Wi-Fi performance quality with my connectivity including ethernet with new generation cables., looking for recommendations and "solutions” but not assumptions please (i.e; microwave of my neighbors who has no idea about Wi-Fi for IoT devices).

Thanks

@ekaya, 

The points of @yalerta and @Jason are still valid looking only at the Wifi part. Even it works great for months if not years. The envorment changes all the time which can influence the speed. 

But since your saying also with a wired ethernet conenction directly to the CPE you dont reach near the 1000Mbps there is somethings else going on. Did you use the Speedtest App to do the wred testing or something else. Can you post some screenshots for the test results. 

Er zijn tal van redenen voor traag internet. Ik stuur je echter een artikel dat je kan helpen het probleem op te lossen. Je kunt ernaar kijken en hopelijk kun je het oplossen. Heb je ook gecontroleerd of er andere gebruikers zijn verbonden met je wifi? Dit kan soms de oorzaak van het probleem zijn.