I noticed that the new actionbar feature for the /title command will overlap with the HUD at the bottom of the screen if the player has enough health bars.

With 3 rows of health bars, the action bar just touches the armor bar as shown in the first image. With more than that, then the action bar begins to overlap with the entire HUD as shown in the second image.

To recreate this, simply give the player armor, health boost at a high level, and run the /title command in the actionbar.