Question about network connections

[Riamus]

I unfortunately don't have access to logs from others and my log shows no errors or warnings, so this is just a general question.  Someone I play the game with will try to host a game.  They have one other person in their house who is playing.  If I join the game (I'm not at their house), the other person there will lag out and can't play but the host is fine.  If I leave the game, they immediately start working again.  If that other person connects to the game from somewhere else, this doesn't happen.  If I host the game, both players at that house can connect without a problem.  I am guessing it's a network problem there but I can't figure out what it could be and was hoping someone may have experienced something similar.

 

A couple notes:

They use WiFi there but if it that was a problem, I'm not sure why it works fine if I host and works fine if they host and all 3 of us are at different locations.

We were able to connect and play just fine in the past.  I know it worked in A20 and hasn't worked since A21.  However, I do not know if it stopped working during A20 or only after updating to A21 since we normally don't play with 2 people at that house.

 

I have had the second person try the network workaround option even though I was pretty sure that was for other network issues and it didn't help.  This is on the pregen 6k map, so it isn't even a very large map.