Try clearing your browser cache.
There's an explanation in https://answers.splunk.com/answers/456802/why-are-searches-stuck-at-finalizing-job-after-upg.html; clearing the browser cache solved the issue for me.
(I was getting the error Uncaught TypeError: _i18n_plural is not a function(…) i18n.js:55 in the Chome Java console).
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