Welcome back,
What payment options do you have available? Have you noticed if the order doesn’t get marked as complete depending on which type of payment is being used? If you haven’t already, visit Events > Settings > Tickets and check the box under WooCommerce Support.

If that doesn’t work, there is an Automatically Complete Orders snippet available from Woo. Let me know if it helps.
We do have a logged report which aims to address the issue at hand. I’ve attached this thread to the report for the developers to reference. You’ll see maintenance release info in your wp-admin and theeventscalendar.com when we get a fix out for it.
Thank you for reaching out and have a good rest of the day.