When you have a popup with so many definitions that the bottom of the popup falls below the screen
and you try to drag up the popup from a point near its top- often, but not always, the bottom of the definition panel will expand as blank space so that you never see the credits (and lookup box). Also if you drag the popup above the upper margin of the display it will disappear when you release the mouse.
Reported by @abrasax
When you have a popup with so many definitions that the bottom of the popup falls below the screen and you try to drag up the popup from a point near its top- often, but not always, the bottom of the definition panel will expand as blank space so that you never see the credits (and lookup box). Also if you drag the popup above the upper margin of the display it will disappear when you release the mouse.
To reproduce: on http://www.thelatinlibrary.com/lucretius/lucretius1.shtml line 8 ponti , line 3 mare, or line 5 solis