PSE 2018: Shift-key to add to selection slow

When I try to add to a selection with the Magic Wand by clicking with the Shift key pressed down, it takes about a second for each addition. When I select 'add to selection' in the Tool Options bar and then start adding with the Magic Wand, there's no problem. But I prefer the Shift-option.

Is this a known issue (can't find it on the forum)? Is there a solution?