Try to group users per role in {teachers}

[bozoh]

Try to group users per role in {teachers}
why not use function get_teachers()

[ebithell]

If no course contacts are set, all roles with the 'manage' capability, which normally includes the Manager role, as well as any set at category-level. These users are then included on the certificate when {TEACHERS} is used. Using get_teachers() seems like a much better solution.
Very many thanks,
Erica