Clicking off or on layers in the TOC that are displayed in the Legend can cause the text symbol size for the legend title and items as well as the point sizes for the patch and spacing between to increase or decrease if A) the anchor point is the lower right hand corner and B) the Layout redraw is not allowed to complete.
allow the draw to complete after clicking on or off a layer or click the pause drawing button, turn on and off layers as desired and then unclick the pause.