It looks like that on your test server the fulltext search class is called, at least that's what I see from the response content. This might be an unknown bug yet, I don't know.
Would you please try to open up the Fulltext search settings submenu and save the options? You can even change them a few times to make sure the input values change. I've checked the relevance code, but it looks all right to me, so this might be the problem I guess.Best,
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