It seems that current version of CiteTools hangs because request "https://tools.wmflabs.org/recoin/getmissingattributes.php violates current Content Security Policy directive. IE. It cant load stuff from wmflabs anymore.
I workarounded problem by disabling the DOI search like this https://www.wikidata.org/w/index.php?title=User:Zache/CiteTool.js&diff=prev&oldid=987095427
Anyway thank you for good gadget.