Hey Mark,
Thanks for reaching out!
None of our plugins provide a “slider” feature, so whichever slider feature you are referring to is either coming from your theme, or from a plugin we do not make.
I would recommend contacting your the theme’s support team for further assistance on the theme slider feature.
If you think The Events Calendar or any of its premium add-ons are related to these issues, can you please specify how? And then also share links to where the failing slideshows are visible online?
Thanks,
George