Looks like the issue is here:
https://github.com/wiki-ai/editquality/blob/master/editquality/utilities/fetch_labels.py#L100
Here's the label where we discovered the issue:
{ "campaign_id": 4, "data": { "rev_id": 637600969 }, "id": 194738, "labels": [ { "data": { "damaging": true, "goodfaith": null, "unsure": false }, "timestamp": 1432144745.16389, "user_id": 42074979 } ] },