The cursor lines (crosshair lines) stay square to the selected plane you are drawing on in synchronous. F3 is the shortcut key to select and deselect planes to draw on, and a lock icon will appear on the right side of your screen when you are locked to a plane. You can use the 'Sketch View' shortcut icon on the bottom right of your screen to automatically move your view square to the plane you are drawing on, and your crosshair lines will be horizontal and vertical again.
The cursor lines in Synch are square to whatever face/plane is located/locked. Check your status bar for options to change the edge of the face/plane to use to set the orientation for odd shaped faces.