I managed to reproduce it in this video.

 

When the Popup Editor is large enough (i.e. after working with a larger item text), it will not show the buttons from its lower part (not the best wording) when editing an item lower in a grid. Since the window is not so easy to move (I have found out one work-around by accident in the video :) ) it can be frustrating when trying to access the buttons and not rely solely on shortcuts (alt+o, alt+c).