Critical error after update to php 8.0

After updating to php 8.0, we get a critical error warning when trying to edit the post type event from The Events Calendar. “Normal” pages and posts works fine. When I set the website language to english, the error is gone, but if I switch back to norwegian as site language, the error comes back. The post type events can be edited when norwegian site language is set and loco translate is deactivated

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