If a block entity is set to render even if its off screen (shouldRenderOffScreen returns true / block entity is contained in LevelRenderer globalBlockEntities), it will also be rendered by the iteration through block entities in visible render sections.
This means that if a block entity is in a visible render section and also should render off screen it will render twice.

I noticed this while trying to render a large transparent box around a block entity, as it was too opaque until I moved my camera away from the block entity.