Question Weird packet losses only on one PC

[ScorpZero]

Hello.

Since some time I've been observing some very disturbing things going on with my internet connection.

The very first symptoms I observed when I had to use Zoom and MS Teams for University meetings. I was just getting weird freezes and audio losses.
At first I thought it could be related to these two programs but nope, my colleagues had no problems with them even with weaker internet connections.
Then I found I also had these freezes and losses during the multiplayer games.

I use 100Mbps connection wired into my PC. And this PC is the only thing on which I see the problem.
I checked a laptop and two smartphones in the same network but connected via WiFi and there were no problems at all - stable connection with no packet losses.

• Checked packet losses via https://packetlosstest.com/ and it differed from 2% to 5% in 180s test - also checked it in safe mode, same results.
• Checked gameplay in League of Legends - stable ping but these packet loss peaks completely ruined the experience, literally unplayable.
• I tracked pings to some IPs like 8.8.8.8 in CMD and PingPlotter and from there it looked rather fine (I could observe severe packet losses on my ISP gate called like BGP.ispname something but I found information on the internet that it's normal - is that so?).
• Tried replacing the connection cable and changing LAN slots on my router but to no avail.
• Tried flushing DNS, renewing IP configuration in CDM.
• Updated drivers for network card.
• Tried utilising options advice from there: View: https://www.reddit.com/r/RocketLeague/comments/601h4e/potential_fix_for_rubberbandingpacket_losslag/
  

I understand that since WiFi connection works fine for the other devices in network then something is very wrong with my PC.
It's all weird to me because other than these losses I have no problem with downloading/uploading files or watching VoD like Netflix or something. There are no breakdowns during that.

Is there anything else I could try before I think about replacing network card or reinstall my system? Or maybe I should contact my IPS first anyway?

Thanks for your help!

 

[ScorpZero]

I ran some more tests.

I took two laptops and tested it via WiFi - everything gone good and clear.
Then I plugged them by the same cable as my PC and ran the same tests (mostly packetlosstest.com). The results were identical as my PC and... yep, severe packet losses.
I tried two other cables, same results - so no cable problem then, I guess?

Hence, I believe something has to be wrong with my Router then and not really with my PC - that's a bit relief, actually.

The router is ZTE F660. It was provided by my ISP as I use fiber internet.
The connection goes with one very thin cable with green connectors on both sides. The cable is connected to green PON slot of my router and to some small white box on my wall.

Any idea whether I can do anything settings related to fix my problem or contacting ISP is the only way to deal with it?

EDIT:
... okay, one more thing to add.

We have two separated lines in the house. The one is mine, the other is my father's. We pays for them separately but both are similar - same routers but different bandwidth.
Anyway, I tested his connection and results are very the same - WiFi is okay, cable connection is completely garbage.

Another thing that comes in my mind is to ask my friend to test his line. He has same ISP and also fiber connection. He claims everything works fine for him in games anyway.