The images are displayed twice.

Him there,

can you share a link to your site so i can see what the issue is

https://www.hcnachod.cz/docasna/

Do you have any custom functions that affect the Post Excerpt?

If not can you check for plugin conflicts by disabling other plugins.

I found that it has a conflict with plugin – Modern Events Calendar.
Can the problem be solved somehow?
Modern Events Calendar is a plugin that I need to keep.
Thank you.