Ok, so sometimes, when I just made a mistake, I click undo once or twice, depending on how many lines it took to make the mistake and wait a second or two. Then nothing happens so i'm like "Huh?" and, naturally as a blonde, I click it like 10 more times, and nothing happens, I think my computer's frozen, but I start to draw, and for each line I make, it undos something from before the mistake, by the time I've made 10 lines, half the drawing is gone. DOES THIS HAPPEN TO anyone ELSE?!?!? If it does, is there a way to do anything about it, besides just pressing redo 20 times? (for good measure, I press it twice as many times.)