Trouble Connecting With Steam Friends

[HogMassive]

I've been playing this game co-op with a friend and gifted the game to another friend of mine because it was right up his alley. When we try to play as 3 people in a lobby that has privacy setting "friends" we get a variety of errors, described here:

One player (A) cannot connect to another (B) at all, getting "host is migrating" within 5 seconds of entering the lobby. Both players in this scenario decide to connect to our third (C) to get around that problem. This worked for 3 hours or so.

The next day we tried the same setup of having C host and connecting. Except now player A gets disconnected, with a message about connection being lost. Occasionally the game crashes or gets stuck on a black screen attempting to join.

So, we tried having players B and C join a lobby hosted by A, and this time player B could join unlike before but player C could not connect at all, getting various errors when trying to enter the lobby, ranging from black screens to messages about failures to connect to the host.

I'm at a loss here. We can all play co-op in 2-man groups, but we cannot play as 3. Are there any veterans that can advise? Tips or tricks to connect with people from the friends list?