The display shows two pairs of linear gratings that translate in opposite directions. Notice that there are two briefly presented flashed lines near the top of the image that straddle the gratings. Also notice the two flashed lines toward the bottom of the image.
Most people report that the flash on the right is above the flash on the left.
Both pairs of flashes are actually physically aligned. You might also try fixating on the upper or lower fixation points, which are in fact precisely aligned with the two pairs of flashes, respectively. The flashes always appear misaligned in a direction consistent with the nearest direction of motion. In several experiments, we established that motion over 50 degrees away from stationary flashes cause the flashes to appear displaced in position. To explain this phenomenon, we have suggested that motion signals distort the representation of visual space.