G2.5b [1073] OS X 10.12.6 – If I select a glyph cell then move to another cell in the Font Window to select a group of cells while holding the Shift key down, if I let go of the Shift key after selecting the last cell, all cells except the last one are deselected. If instead I continue holding the Shift key down for about five seconds, all the cells will remain selected. I tested this a half-dozen times being careful not to accidentally touch the mouse at any time after the last selection.