How to fix the problem with the drop in the Internet on 1 device?

Question

Computer networks

The problem is that on the 1st PC in the house, the Internet speed drops so much that tabs in the browser do not open, the game freezes, during Internet calls (in Discord) the interlocutor is heard, but I am not. The problem manifests itself every few minutes (chaotically) for 4-7 seconds and starts working again.
The PC is connected via lan cable. The rest of the devices are working properly. In network diagnostics through the task manager, it shows a sharp decrease in the Internet and a reverse recovery.
The icon always shows that the Internet is available. Provider Rostelecom. They called, problems with the equipment in my house and those. they don't have jobs. There is the latest version of the driver on the network card.
This problem happened this fall. I decided to change the TCP and UDP protocols
(UDP 27000 to 27015 inclusive (Game client traffic)
UDP 27015 to 27030 inclusive (Typically Matchmaking and HLTV)
TCP 27014 to 27050 inclusive (Steam downloads)
UDP 4380)
Today the problem showed up again. They didn't change anything. Didn't download anything on pc.

Answer 1

Download and run WinMTR diagnostics on 8.8.8.8 eg
Parallel to any other host closer to the ISP - ideally something two or three hops away from you.
So you will understand where the problems are.

Answer 2

Estimate external channel load, estimate the channel load to this PC. Run a long ping to the router, in parallel to the provider's gateway and to some public resource, see if there will be packet losses, if so, will they coincide in time on all three ping "sessions".

Answer 3

Try a different router port, try a different cable, try a different OS (all this after turning off all other devices in order to exclude their influence on the channel bandwidth). If all this does not help - apparently, the matter is in the hardware of the computer.

Answer 4

Possibly strong RF interference
Possibly short in connector Re-crimp connectors