@devnihil I confirm you i’m using wordpress 4.9.7 and Yoast v 7.8
When i activate the plugin, it deletes all the theme configuration (every single configuration, logo, images, custom css, footer, etc).
I try to restore that configuration by importing it from backup and it doesn’t work. Nothing happens. If I deactivate Yoast, then i can restore the configuration and the import works as it should.
The theme (monolit by CTH themes) uses Redux Framework to manage the theme options. I don’t know if it could be the origin of the problem.