Hi Simon,
Thanks so much for reaching out!
We have since changed the wording there from local timezone to manual timezone, so that is the setting that you should enable.
If you are still having issues with Eventbrite Tickets, as a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Let me know if you have any other questions in the meantime!
Thanks,
Jaime