Thanks for the topic. Hope you are having a nice day.
You need to check if the problem will be solved if you activate parent theme on your site (Appearance > Themes).
Try to disable all 3-rd party plugins and then check the image gallery. Let me know results.
Also, you need to update all plugins – https://www.8theme.com/download-plugins/ (To update premium plugins, connect to your server using FTP. Copy extracted plugins folders into wp-content/plugins/)
If the problem won’t be solved, provide FTP access in Private Content.