dear sir
good day to you!
hope you will be fine, please provide the reply for the following
If the issue is happening because of Next-Gen display option it means that your theme does not handle <picture> tags as same as <img> tags. When using Next-Gen display option (using <picture> tags), the HTML output is changed by wrapping up <picture> tag on top of <img> tag. The CSS code that handles <img> tag is not applied properly in that case. It would be ideal to contact your theme provider and ask them to check this in more detail, as it would be great improvement for their theme to make full compatibility for using picture tags.
thank you sir