There is a bit of an odd problem that really isn't a major issue, but could lead to some confusion. It requires multiple players to reproduce. Start with the first campaign, invite players have them join this first campaign and remain in the campaign through out this reproduction scenario. As the GM of the first campaign, go into campaign setting and Copy/Extend Campaign. In my reproduction the only thing checked during the Copy/Extend Campaign was the "Players and Player Settings (Including Macros)" option. Log into the second campaign. In this second campaign you will see that all of the players that were joined to the first campaign are listed as active participants in the second campaign (their names show up as joined to the campaign along the bottom portion of the campaign window), however they are not really there. Their names will remain there until they log into the second campaign and subsequently exit the campaign (even if they exit the first campaign). Again, very simple solution, but it is a bit strange to be extending a campaign and begin working on it to see people already connected when you join it.