Good evening and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the fact that you are getting an error 500.
I would love to help you with this topic.
I believe you are referring to this snippet: https://theeventscalendar.com/knowledgebase/moving-the-ticket-form/
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/
Could you please send me a copy of your WordPress theme / child theme in a .zip file link (via Dropbox or Google Drive) so that I can run some tests on my end ?
In the meantime of course, you could restore your site by removing the snippet.
Best regards,
Geoff B.