See this line -
```rust
challenges: ctl_data.challenges.challenges[i % config.num_challenges],
```
This doesn't work if we have multiple lookers from the same table; then `zs_columns` will contain multiple contiguous entries for the same challenge.
We could fix the index calculation, but it seems a bit error-prone. Seems easier to store the specific challenge as part of `zs_columns`.
8e220ac623