Teacher not displayed in course list

Dears, many compliments for your excellent job! Coming to my question, in the course list page (/my-courses view) instead of the teachers, the following token appears: "Teachers: node_og_membership_nid); ?> " In the course group page the teacher appears to be active and it has the role teacher. This strange problem only shows up in my localhost distro installation, and not in production. I think that it might be very insightful to understand why this is happening. Many thanks, Pietro