>different key combinations for the first time you undo and the second time you undo. That's not what's going on. Ctrl+Z is an undo/redo toggle, Ctrl+Shift+Z s

>different key combinations for the first time you undo and the second time you undo. That's not what's going on. Ctrl+Z is an undo/redo toggle, Ctrl+Shift+Z steps back in the document history. You shouldn't do Ctrl+Z followed by a series of Ctrl+Shift+Zs. Just do Ctrl+Shift+Z.