Displacy visualiser only sometimes shows labels

In many cases, I do not see the label at the beginning of a span in displacy. This should not be an issue with a particular label since I sometimes see it when using different text examples.

Is there something I should look out for to avoid this?

```
colors = {#omitted in this example}
options = {"spans_key": "sentences", "colors": colors}

displacy.serve(doc, style="span", options=options)
```


Thanks!