Related Questions:
My Event information isn't showing
Event merge field isn't working
There is a bug in my email template
The {{event.name}} and {{event.startDate}} don't appear
The merge fields that I've added into the email template are pulling the information from the wrong event.
Answer:
When using Event merge fields on an Email Template, it's necessary to select which Event you'd like to use:
If you do not select an Event from the dropdown, the default Event for the Email will be the Event with the earliest start date/time. If all Events have the same start dates/times then the selection will be random. To ensure you are pulling the correct information, please choose an Event from the dropdown list as shown.