my characters got 100 xp when starting the game coming through the portal, now when I log them in they get 100 again for entering the ziggurat
Are you sure it didn't just happen after the new module update? I got 100 xp for logging in after the update, too. If it KEEPS happening, then it's a bug.
yeah when the dm make a change the the area. you usually get 100xp for discovering it again. only once per char mind.
This usually is a signal that there's been a major update to that area in the module, as Pup says.