Hey Toby,
Thank you for reaching out to us!
I’ve just tested the [tribe_events tribe-bar=”true”] shortcode in my own site and wasn’t able to reproduce the issue you are experiencing.
To get started I would recommend you to make sure that both Events Calendar and Events Calendar PRO are up-to-date. After the plugin update, if the issue persists, I would recommend you to run a Conflicts Test. You can start the test by temporarily deactivating all of your plugins (except Modern Tribe plugins) and changing your theme to another one like Twenty Seventeen and let us know if the problem is solved after that (don’t forget to backup your database before changing anything).
If you have any other questions in the meantime please feel free to let me know and I’d be happy to help as best I can!
Cheers,
Patricia