The Trauma card "All Alone" says that: "Each time you enter a room containing another investigator, or one enters your room, test your Willpower. Fail: Take 1 Horror."
I had two investigators walking through a mansion essentially hand-in-hand when I gave one of them this card. Is there ANY way for them to stay together and not be triggering this card almost every turn? It seems silly for one investigator to be making a Willpower check almost every turn solely because the game mechanics require one invesitagor to move AND THEN the other one to move, when in reality they would be walking together.
The compromise we came up with was to forego the Willpower checks as long as the two investigators were never more than one space apart. So, the one investigator stayed sane at the cost of severely slowing down the movement for the pair of them.