Sierra 10.12.6, G2.5.2 [1186] – When opening a character window, there is a brief flash of the character as if the space bar has been pressed to preview it. It lasts about one second then the outlines quickly shift down all the way to the bottom of the screen leaving only the top of the outlines visible. This is consistent, happening in each new character window that is opened.
Same on Mojave.
I am curious what you changed recently, Georg. Seems you’re retouching major parts 
That is the preview area flashing before it is minimized.
No, the issue is that the glyph is scrolled down (almost) out of sight. My preview styas where it is.
same here