Components added from libraries in the sidebar are added above the frame and not contained within the relevant frame. This means that you need to navigate back to the layers panel to manually place the component within the frame every time.
- Open design file.
- Select frame
- Navigate to Assets
- Search for a component in a library
- Click on component.
- Insert instance.
- Observe that the component seems like it is in the frame.
- Navigate to File.
- Observe that the component was added above ALL layers.