Interesting. When I preview your file, there is data in the bottom line of pixels as you intended. However, when I open the file in my animation editor, all of the frames are missing the bottom line of data. As if the information defining the boundaries of each frame subset are one line short on each frame. Yet the last line of each frame is there, since some programs display it correctly. I think it's a bug in your GIF creation program. Which one are you using?

An additional bug in your animator program is that it leaves a zero delay on each frame, instead of inserting a 80-100ms delay between each frame.

When I open and re-save the file using the Jemplode animation editor, the resulting file does not have the problem, and has the correct frame delay: