Updating product image

Propably you replace only original versions of images, but wordpress create a few this same images with different sizes. After upload your photos you should regenerate thumbnails on wordpress dashboard. You can use for it: https://pl.wordpress.org/plugins/regenerate-thumbnails/ or little advanced: https://pl.wordpress.org/plugins/regenerate-thumbnails-advanced/ When you regenerated thumbnails, images should be correctly displayed.