Hello,

This issue caused by you've enabled lazyload images/media from a plugin like SG Optimize or Jetpack or a3 Lazyload or another plugin supports lazyload images. Let's check and disable this setting/plugin. Because by default, the theme already supports lazyload images from itself.

In case you want to use lazyload images from your plugins, you can deactivate lazyload images from the theme via Customize > Speed Optimization > General & Lazyload >  and disable all lazyload images from the theme there.

Best Regards.

PencilDesign