Search results show posts not containing keyword searched

I’ve double-checked I have my search settings set properly and re-indexed the site. I keep finding instances where a search result does not contain any trace of the keyword searched. Often the keyword is in the post’s author bio, or perhaps in one of the related posts or previous or next posts displayed under the post content, but not in the post itself.

For example, this is the top 10 search results for the term “injury”: https://velletta.infinitemonkeys.ca/setting-up-a-sole-proprietorship/

Is there any way to fix it so it indexes properly?