Read a setting I turn off at https://www.howtogeek.com/224981/how-to-stop-windows-10-from-uploading-updates-to-other-pcs-over-the-internet/
To fix this however you have to get everyone to turn it off and reclaim your network traffic.
-> The "connected through electricity" clue is interesting. Just recently another member battled this and after a lot of trials we found that swapping the two powerline modules the speed returned.
After this I thought of something else that we can try. See if the powerline modules have firmware updates.
Hey there, recently I have noticed that the internet connection in my computer is getting to 1 or 2 MB/s some days and it gets to 10 maximum,although its constantly 20 to 30 MB/s for the others in my house.
They are using wireless connection for their laptops, however, I'm using a Lan cable, which is not directly connected to the router, but its connected through electricity (the router is connected to a cube(Edimax HP-5103) and my pc too) because the router is far away from my pc.
This problem is either because of the cubes o,r as I think, because of my computer.
In my task manager, network is at 0-2 % even if I'm using and there are some service hosts running in it.
Thank you for reading this and I appreciate it if you could help.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic