We're going to test something shortly and then roll out a fix. I'll keep you updated.
Edit: To Update we're testing a fix through the night and expecting to roll something out tomorrow morning. Will have another update in around 12 hours
Edit 2: More Update. Fix looks good, hoping to roll something out later today now as we've correctly identified that we can solve the issue preventing the award from being granted, but also need to seperately solve the task of identifying all users who completed the task but were not rewarded and address that seperately.
(5/15 - 11:20 AM Sweden Time)