To test:
- Create an extended patron attribute, for example: proxy
- Make sure it's marked as searchable in the configuration
- Add the field to a patron, example: surname, firstname
- Search for: 
  - surname: works
  - firstname: works
  - surname, firstname - doesn't work
- Change the entr to: firstname surname
- Search for:
  - firstname: works
  - surname: works
  - firstname surname: works

The problem appears to be searches containing a comma.