While zooming in and dragging a categorical boxplot, I got in a state where the longer labels of the horizontal axis, that are displayed in an angle, overlap the horizontal axis title. To get to this state, one has to zoom in so that only shorter labels are displayed oblique, then drag the plot so that a long label appears in the corner of the plot, without getting over the axis title. I noticed that the title moves upper when I leave my mouse button. Then click to drag again until the longer label is over the axis title.
If from step 1 I drag more so that the longer label is over the axis title, and I release the mouse button, the plot moves a bit up so that the label does not overlap the title.

Step 1: zoom in to only see short labels:

Step 2: drag to the right to make a long label appear on the left:

notice the title moved upper (this is important in order to reproduce) instead of staying on the bottom of the div

Step 3: drag to the right so that the long label overlaps the title

From step 1, if you drag directly to a position similar to step 3, you'll get into a state where there is no overlap: