I killed all of the Uber bosses, and Uber Lilith (up to T3) and still got no spark as a reward.
Yep I just killed her in a group and didn’t get a spark while my partner did. When I checked it said that there was an update for D4 so that might have been the issue. Otherwise it’s bugged.
Yep, happened to me multiple times today while other party members received their rewards and it is certainly a bug requiring resolution.