Plugin suddenly breaks my site

I was enjoying life setting up a blocktheme with Blockera and it looked great. But… all of the sudden, I recieved a “There has been a critical error on this website.” error. Admin page works normally, except for the site editor (Appearance>Editor). That’s giving me a “You attempted to edit an item that doesn’t exist. Perhaps it was deleted?” message.

When I disable the plugin, everything returns to their non responsive mess, but at least I can access it. Please help, I miss Blockera.

The page I need help with: [log in to see the link]