The Help > About window has some issues with resizing. When you first open the window it smoothly expands itself to be ~50px wider over the course of about half a second. Clicking through the tabs or scrolling causes the window width to ratchet up incrementally with each click. These increases stop when the window is about 600px wide. The window can't be manually resized to be narrower and must be shrunk through the clawsrc file. By clicking and dragging to resize, you can see that you can't make the window narrower until it's grown to wider than ~1300px.
I've never seen any of the ratcheting up, but I cannot shrink the window, only make it larger. It seems to be a problem with having scrolled windows as notebook pages. That is, a GTK3 bug.