Question Packet loss only with other people from my isp

[zeboftw]

Me and my friends tried playing some multiplayer games. I hosted a server but they would randomly get disconnected. I realized this was only happening to people who have the same isp as me. And the problem persists the other way around. If they host and I join them I would get randomly disconnected withing 10 minutes.
If the person hosting is from another isp there are no problems. I tried pinging them and with people from other isp's I have close to 0 packet loss but if we have the same isp I get about 3-5% packet loss.
One thing I have not checked is if it happens between other people aswell, if someone else from my isp host and other people with my isp join will they have the same problem? I am looking into that right now but I can't get my friends to be available at the same time.

 

[Ralston18]

Which multiplayer games? Same problem with all games or just certain games.

Who is the ISP? Helpful to know as someone else may have some direct knowledge of or experience with similar problems on that ISP.

What make and model modem and router do you have (or modem/router if only one device). ISP provided?

And continue with "One thing I have not checked is if it happens between other people aswell, if someone else from my isp host and other people with my isp join will they have the same problem? "

 

[zeboftw]

So far I have experienced this with Killing Floor 2, Hearts of Iron 4, Minecraft, Rimworld, Risk of rain 2.

My ISP is UPC, I think they're mostly present in Eastern Europe, I haven't heard about them in other countries. They provided the router too, I think it's custom made by them, it's called Connect Box.

I have gotten one of my friends to do a ping test and he has no packet loss when pinging someone else from UPC.

I don't think the problem is between me and my router since when I ping my router I get 0 packet loss. Some random packets do seem to be slow, on average each packet is delivered in 1 ms but sometimes it will take 100+.
I have also tried ping tests from a laptop connected through wi-fi and it's the same problem. Good connection with anything but other people on UPC.