Can't get JSON using search, just get [] brackets

I’m struggling to get JSON using the API to search.

Posts are fine as below:

http://oxfordwords.staging.wpengine.com/wp-json/wp/v2/posts/38426
http://blog.oxforddictionaries.com/wp-json/wp/v2/posts/38426

But I can’t seem to get any using Search

http://blog.oxforddictionaries.com/wp-json/wp/v2/posts?search=word

Any ideas?

Search works on our test blog
http://wp.magicalbytes.co.uk/wp-json/wp/v2/posts?search=word

And I can get JSON when searching for nothing http://blog.oxforddictionaries.com/wp-json/wp/v2/posts?search=

Any help much appreciated. Staging blog is on the latest version of WP and the latest version of the WP API Plugin is installed

https://wordpress.org/plugins/rest-api/