Here's the culprit! The loop goes through node children, but if the child bbox fits into the search area, you're then running `_all` on the whole node instead of just the children.

Rewriting this line like this fixes the issue and provides ~3x improvement of 10% searches in my tests:

```js
if (node.leaf) {
    result.push(child);
} else {
    this._all(child, result);
}
```