There has been a problem that has been happening to me for the last few month, I would like to finally ask about it on this forum.

There is another user that would often play in the same game room as me, but before he joins the room, all of my connections to other players are direct. As soon as he joins, the room will say my connection to all the other players are unresponsive and then becomes Fast Proxy connection. I do no think this is a coincidence, this problem can be reliably reproduced every time when he joins a room I am in/I join a room he is in. I almost never see FP connections between me and other people otherwise.

Despite the room saying I am on a FP connection to everyone, when in game, the game runs without lag with small ping. However there are times where I would be expelled from a room because I am shown to be FP when in a room with this user.

Here is the link to his profile:
https://www.voobly.com/profile/view/125112843

I really would like to understand what is causing this. Thank you in Advance.