When running Repository.Query command on Playground it works properly. Then I was playing with CURL request generated at Playground CURL Request UI tab it failed.

Returning a really unhelpful message

{"entity-type":"exception","code":"java.lang.NullPointerException","status":500,"message":null}

It took me a while to figure out the issue and it ended up being the lack of Content-type header.

Adding -H "Content-Type: application/json" fixed and provided the proper result.