|You can restore images in frames of optimized GIFs with help of menu item File / Restore Frames.
Note: in common case we unable to define exact frame that contained the pixel before optimization. Another problem that two transparent frames may have different 256- colored local palettes, so we have image with more than 256 colors and must make color reduction. Sort color map by usage and remove unused entries. For more images, not being photos, the amount of colors used for reproduction frequently is less 256. So it is possible to remove them without any loss for images.
Note that color palette may contain one of the following number of entries: 2, 4, 8, 16, 32, 64, 128, 256. It means, that after removing unused entries size of color palette may be reduced, or may be not. It depends on the number colors in source palette and number of unused colors in image.
Look at two GIFs - they do not differ, but left image uses a full color palette in 256 colors, and right image has palette consisting only of 32 colors. And also these images have different file sizes.