The new GUI of 19w11a is cut off on the right by one texture pixel. In vanilla textures this is the black line column farthest to the right.

Screenshots to show both vanilla and skinned.

Also while we are on the subject and because the Feedback site is pretty worthless, forcing the new GUI to use the widget textures is a really bad design choice. They should be part of the GUI texture itself like the rest of the container GUIs.