Hi,
it would be helpful to know what is the exact error you get. But from your snippet, I'd say that you're getting a json_parse_exception, because Mustache is trying to escape the {{query_string}} tag.
If this is the case, you need to avoid automatic escaping by using the triple mustache (see: https://mustache.github.io/mustache.5.html), like in the snippet below:
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