It was reported to me by a client that a s2Member-List search with orderby="last_name" was not sorting the found list by last name. Instead it was sorting by first name. I happened to read https://forums.wpsharks.com/t/s2member-list-shortcode-search-parameter-causing-other-parameters-to-be-ignored/1608/3 by trev800 that if you remove orderby="last_name" it worked OK. But I don't think it is actually working. I think it's sorting by user_id instead.
Although the original list looks OK, you can see orderby="last_name" here when you do a search.
Here's the original shortcode that used to work:
[s2Member-List enable_list_search="yes" show_display_name="yes" show_avatar="no" show_fields="Degree(s):degrees,Licenses/Certifications:licenses_certifications,Address:street_address,Address 2:street_address_2,city,State/Province:state_province, Department/County:other_state,Zip/Postcode:zip_postcode,country, phone,Address:street_address_b,Address 2:street_address_b_2,city_b,State/Province:state_province_b, Department/County:other_state_b,Zip/Postcode:zip_postcode_b,Country:country_b, phone_b, office_hours, Email: user_email, website, Areas of Specialization:specialization" template="member-list.php" limit="50" levels="1" ccaps="r" orderby="last_name" order="ASC"/]
Please help. Thanks.