In Timetable Manager > Manage Lesson Schedule it is possible to assign a member of staff to a lesson despite them not being set as a member of staff for the associated subject. This can lead to issues completing reports later on.
When adding or editing a lesson, run a validation check to ensure that the member of staff selected is set as a teacher for the associated subject for the set/form. If the validation fails offer the following options:
Add teacher to subject
Continue without adding teacher to subject
Cancel