Product Slider data is null when use manual assignment

Hi everyone,
I have a issue with the product slider.
First issue: In administration, i added a product slider that using dynamic product group and a product slider that using use manual assignment.
I created a my resolver class that inherit from ProductSliderCmsElementResolver for loading data on storefront.
But on Storefront only display data from dynamic product group , data from manual assignment is null.

Second issue: On Storefront can’t display product’s cover (I still using Product Slider). Do I need to do anything at resolver class ?

Thank everyone.