Version: 4.7 P8
Platform: OS X.10
If the editor is in the background (e.g. another window in front of it, or simply when some other app has the focus and it has reduced it’s framerate), if you click any button (e.g. the dropdown for the Play button, the UMG designer anchor button) it will make the editor go into an infinite loop, making you force quit it.
For this not to happen, you need to first focus the editor (e.g. clicking inside the game view or on the window top border).