Xbox one says 100% packet loss? Not sure if that's the cause. But my nephew (the one using...

So to start id like to give some info

Me an my nephew are in the same house, on the same wifi/router, using a wired connection. I've checked to make sure the nat types on both are open (they are).

An yes the games were having the issues with are cross gen. (Xbox one s can play with Xbox series s/x

I've tried resetting Xbox. Uninstalling an re installing said games. Making sure everything was updated to current updates. (Both said games an both consoles)

An I reset an power cyled router/modem. An made sure everything is going good on there end. An no other electronic/devices including my other series s an my original Xbox one launch model are having these issues. An they not even using a wired connection. An I don't think it's my series s either.

NOW with all that out the way. HERE IS THE ISSSUE:

So my nephew on his Xbox one s. Is connected to only thru a wired connection, he can go online, play games online, join others lobbies etc. An in some games he doesn't have any issues at all.

But as of late. In Monster Hunter world/icebourne a game we've played together before for almost 2 months straight..we know have come back to after a year..to find out..he can create a lobby, or.join others lobbies but cannot join mine (says fails to connect to server or lobby if he tries to join me) an if he invites me...it tells me same thing (failed to join/connect to lobby/server if I try to join him) but then sometimes I do get to join..BUT THEN ONCE IM IN HE GETS KICKED/DISCONNECTED (the game tells him, he's lost connection to the server/lobby) AGAIN id like to point out we used to play together on this game all the time. Him join me or I join him no issues, an we also play MH rise daily with no issues either.

Now I would dumb this down to just Capcom issue..BUT we've had a similar issue with borderlands the pre sequel.

Now we've played all of borderlands 1 for a month straight, no issue he always joined me. BUT when we went to the pre sequel, he cant join me..only I can join him (if he tries to join me tells him he can't connect or lost connection).

AGAIN we don't have this issue with Border lands 1.

Now I've already listed all the things I've tried..

But only logical think I can think may be the issue.

Is sometimes when he would run a test or multiplayer connection test it would tell him something about a usnp failed to connect (or something like that) or that he had 100% packet loss.

BUT AS I SAID even with these things.

He would still be able to be online, play online..an join others..he can't join me..an if I join him..he gets disconnected from the game? Or possibly the Xbox live for a second..Wich is why the game says he lost connection.

WHAT DO I DO, THIS IS SERVERLY ANNOYING.

:)