Highlight field is empty

Hi all,
I'm using the https://search-api.swiftype.com/api/v1/engines API and I'm concern about why for some results the highlight field comes empty, that field always should return values right?

I was reading the documentation : Highlight Fields | Swiftype Documentation

Any thoughts about it?

Probably best to ask in the App search forum

I expect it's down to a doc result based on a fuzzy match and not handling highlighting well.