Good evening Jonathan and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
We are sorry to hear about the struggle you have been experiencing with the iCal plugin.
I would love to help you with this topic.
What is going on is that the plugin keeps a trace of all imported events (UID) to make sure these do not get duplicated when running the importer again. In fact, a trace is kept even after deleting them from the backend.
Your best bet (after a database backup) would be to remove these traces prior to running the plugin again. You can do that in a couple of ways:
- Manually going in the DB and removing the saved entries in the WP_posts table
- Using the following snippet: https://gist.github.com/niconerd/62617b7f5cecb9ae609f#file-clear_deleted_events-php
- Using a DB cleanup plugin such as https://wordpress.org/plugins/rvg-optimize-database/
Let me know how that goes.
Best regards,
Geoff B.