Great post :)
I encountered this today. After restoring an EBS snapshot the problem had gone away. I compared my wp_options table from the backup and found the elementor_active_kit option was different.

select * from wp_options where option_name = 'elementor_active_kit';
+-----------+----------------------+--------------+----------+
| option_id | option_name | option_value | autoload |
+-----------+----------------------+--------------+----------+
| 169 | elementor_active_kit | 5 | yes |
+-----------+----------------------+--------------+----------+

I found this post, confirmed the issue switched it over and the site was fixed!
Curious to know if any of the people here have some common plugins. My initial thought is that perhaps some page duplication plugin is duplicating the default kit with it perhaps?

Thanks again.