Upon completing Lord Batfort's Manor the first hero in my party the fighter, which has always been slightly ahead on exp, did not receive any exp upon completion of the adventure. The second and third heroes did with the second hero triggering the major power token tutorial. I relogged and the problem remained the same, the first hero is still at level 14 18/20 while the second and third heroes are at level 15 2/20. I tend to click rapidly during the adventure complete / loot screens not sure if it managed to somehow hurry up past the awarding of exp.
The key is "slightly ahead on XP." The XP you get depends on your level relative to the adventure's level, and so it's entirely possible for a character who's behind to suddenly jump ahead: all you need is for your characters to be on opposite sides of a level divide. We've had a lot of threads before where people miss the exact moment this happens. For reference, here's an XP chart. Compare every individual character's level to the adventure's level, and if you are . . . There was some point where I calculated what it took to get your starting three characters, who all have different amounts of XP after the opening missions, to have equal amounts and avoid confusion. Unfortunately, I've lost track of where that was.
Thanks Sir Knight that is useful info to have. I must have missed when the later characters pulled ahead on exp.