Your colleague created a line item in Display & Video 360 for their clients’ mobile web campaign and targeted mobile in-app by mistake. They went in and removed the mobile in-app targeting at the insertion order level, but the campaign is still targeting mobile in-app. Why is this happening?

You can’t modify insertion order targeting at the line item level.
You can’t modify targeting for mobile in-app inventory.
You can’t modify targeting once the campaign has line items assigned.
You can’t modify existing line item targeting at the insertion order level.