Incorrect value type ‘@context’ — no solution?

Hi there,

first of all, thanks for reading this!

Out of a sudden, Google Search Console has emailed me with this issue. I’ve done my bit of research and thought Minify HTML might be at fault. However, after deactivating the plugin and validating the fix, the same error popped up.

I’d be grateful if anyone could suggest other culprits.

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