As with other templates, the Event template must be validated prior to running. Attempting to Save or clicking the Validate button will run through all the validation checks for the loaded template.
If validation issues are found they will be displayed in a list categorized by their severity. At the end of each issue will be a dropdown list which will provide hints as to how to fix the issue. Clicking the Find button at the end of the row will attempt to automatically located the component and highlight it for you.
If the error is critical and prevents the template from serializing then your template cannot be saved until the issue is fixed. Errors will allow your template to save but not run. Warnings and below are recommendations but do not block you from moving forward if you choose to do so.

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