User Selector role filter problem

One of my tables has a User Selector field (recruiterID) that is filtered to be visibile to three roles (Recruiter, Recruiting Manager, and Recruiting Director). However, I have one user who, despite being assigned all three of these roles, will not appear in the selection list.

Removing the role filters from the user selector field will allow this user to populate in the selection list, but when I add one of them back, he disappears from the list. This does not seem to happen with any other users.

I have tried deleting and recreating the field, and deleting and recreating the user, without success.

Any thoughts on why this might be happening?