The Search & Filter Pro Text Search field uses the standard WordPress search, so looks only in the Post Title and Content and behaves the way you describe. To help you control this better, on the form’s Advanced settings tab you will see 2 settings for Relevanssi.

The documentation for this is here:

https://www.designsandcode.com/documentation/search-filter-pro/3rd-party/relevanssi/

You would need to install and activate the free Relevanssi plugin as well.

Then set it up (in your case change the Keyword Matching) and build its index (make sure it is indexing the desired post types AND the taxonomies/custom fields that you want to search). See this screenshot:

https://www.screencast.com/t/FNtqfaW0jg