title: NSWindow drag regions should only be invalidated on the Main Thread! This will throw an exception in the future
body: <p>I am writing a Python program with two threads. One displays a GUI and the other gets input from a scanner and saves data in an online database. The code works fine on my raspberry pi but if I try it on my MacBook Pro (Catalina 10.15.2), I get the above mentioned warning followed by my code crashing.</p>
  <p>Does anyone have an idea how to get it working or what causes the problem?</p>