Has it happened before the EASA and the FAA disagreed on the airworthiness of a plane?
It seems FAA and EASA did disagree since 2016 about 737max certification, and not just after the crashes. EASA certification was conditioned by training and more information to the pilots, which hasn’t been done. 

Please refer to the following website:

https://www.cnbc.com/2019/03/29/reuters-america-insight-regulators-knew-before-crashes-that-737-max-trim-control-was-confusing-in-some-conditions--document.html

You read the following:


  The European Aviation and Space Agency (EASA) certified the plane as safe in part because it said additional procedures and training would “clearly explain” to pilots the “unusual” situations in which they would need to manipulate a rarely used manual wheel to control, or “trim,” the plane’s angle.


You may also read about EASA:


  The undated EASA certification document, available online, was issued in February 2016, an agency spokesman said:
  
  It specifically noted that at speeds greater than 230 knots (265mph, 425kph) with flaps retracted, pilots might have to use the wheel in the cockpit’s centre console rather than an electric thumb switch on the control yoke.


So when agencies give their approval it doesn’t mean the approval conditions are the same, it was not the case since the origine  for the 737max, and not just after the crashes.