Error when adding more assignments

[anya-ji]

I get this error when I tried to add more assignments. In hit_ids.json, the last HIT has 2 assignments and the rest have 9. I was able to add more, but at some point it starts to give me this error…
I created another folder with the same setup and uploaded again and that one doesn't have this problem, but I just can't add to the old one without getting that error. Any idea why? Thanks!