I completed season 1.5 chapter 1 right at the time of the goal-bug, so I got the prize but when the bug was fixed the goal was left as incomplete. I didn’t give it much importance since I did collect the reward. However, now after completing Chapter 2 this happened:
It seems that “Complete Season Chapter 2” does not look for that chapter’s completion, but it triggers upon chapter completion instead. And since the chapter 1 is not registered as completed… Then I cannot claim the reward.