How do I clear local calendar events cache and re-sync?

I recently started using a Nextcloud instance for my calendar events. I am able to sync events so they show up in the GNOME Calendar app, but there are many duplicates. Is there some place where events are cached locally where I can examine them or clean them up?

The events display properly in the Nextcloud Calendar app -- I don't see any duplicates. I only see the duplicates in GNOME Calendar.

I looked in locations mentioned in In what file does gnome-calendar store calendar events? but I didn't see any actual calendar event data, just references to the calendar webdav URIs.

I tried deleting and re-adding my Nextcloud account in the "Online Accounts" settings dialog. I tried disabling and re-enabling Calendar synchronization for my Nextcloud account.

I'm using:

• Ubuntu 20.04 LTS
• Nextcloud 19.0.3 (latest stable)
• GNOME Calendar 3.36.2

Looks like they are in SQLite3 databases under ~/.cache/evolution/calendar/. I was able to trash that directory and it automatically re-sync'd. Yay!

The duplicates still exist; this separate issue might be with the Nextcloud database. I downloaded the ics file for the calendar from Nextcloud and I do see what appear to be duplicates in there.