Dear support team,
One of the main Sydney plugins (SiteOrigin Widgets Bundle) caused a bizarre error after their 1.15.6 or 1.15.5 updates (not sure which of them caused the error).
I was not able to solve it by merely deactivating the plugin, as it seems to be one of the core plugins on Sydney.
For now, the solution I found was installing “WP Rollback” plugin. I used it to get back to SiteOrigin’s 1.15.4 version. It worked, but please take a look at this issue. This is how my site became after the SiteOrigin latest update: