Adding new layers to a gif?

I'm tweaking a short animation I recorded and am trying to add shapes on top (like a watermark) and want it to be in the same spot throughout the timeline. I always select the first frame so the effects of what I'm adding equalize across all the frames. This time though, when I'm moving a shape into place, it's offset in the rest of the frames but fine in the first one. What's the proper way to apply layers uniformly across all frames? I tried grouping the frames' layers into a smart object but that overode the frames and it became a static image of the first layer 😕😕

Hack work around: duplicate the layer into a new file, delete layer, duplicate that layer back into the original file. xD