I tried to check the website's homepage, but it was protected with a username and password. I checked the website's debug information and saw more than one plugin for sliders. Please let us know which plugin was used to build that slider so we can recommend the next steps.
If still an issue persists, please provide temporary access (WP-Admin and FTP Login info) to your site (preferably staging site), so that I can look into your setup and debug the issue.
Your next answer will be private which means only you and I have access to it.
=== Please backup your database and website ===
✙ I would additionally need your permission to deactivate and reactivate Plugins and the Theme and to change configurations on the site. This is also a reason the backup is really important.