When using a custom employee reference field, an error could occur where the planners are not set up accordingly to the hierarchy of the employee reference field, and instead shows every employee without structure.
This occurs when there is a "loop" in the reference field, meaning the field does not have a well-defined hierarchy.
To solve this, create a report using the Directory of the employee reference field, and check if the reference field does not have employees that have that reference field on themselves or stuck in any hierarchy loop.