When hitting 'reply all' in a the private message of a game either there are no names selected or what appears to be a random selection of names that are not in the private message thread selected.

It is apparently happening to several people as some others in the game are complaining of similar issues.

Probably best to rMail the mods with the name of your game so they can take a closer look, unless someone else is having the same problem in a different game.