I have a search page set up with a shortcode like this:

[civicrm component="profile" gid="18" mode="search" hijack="0"]

Everything seems to be working except that searching on a custom data field, "Certification," generally isn't working.

None of the other search fields are custom fields. Don't know if that relates to the problem.

You can try it out here:

http://connectionpractice.org/trainer-coach-search-page

------ new material below, added in response to comments -----

"Certification" is a text field and is set to "Searchable."

Some examples of content for the "Certification" field are shown below. I would expect that I could search on any string within any of these (e.g. Curr or Curriculum or Teac or Teacher). None of those work. Even searching on a complete entry like Coach, Trainer/Teacher, Curriculum Instructor doesn't work. The only one I've found that works is Coach -- I'm guessing because that is a complete entry with no commas? Perhaps the commas are causing the problem?

Wordpress 4.7.5 CiviCRM 4.7.17