This happens for me whenever the scale doesn't evenly divide the canvas size, what do those settings look like for you?
I think perhaps when exporting, the program doesn't handle fractions of pixels, so some frames end up wider than others in the spritesheet, as the fractions build up and eventually are more than one. Inconsistent frame widths is what leads to this weird scrolling effect when playing the gif.
What fixes this for me is when I make sure the canvas size divided by scale results in an integer. If you want a 16x30 sprite and your scale is set to 4, try setting canvas size to 64x120. Does that fix it?