Why would a sprite animation frame have artifacts?

I have a sprite with about a dozen frames (they are simple shapes - diamond, circle, square, etc). Certain objects create artifacts when they are not animation frame 0.

For example,

Notice the right of the diamond in the top sprite. This is frame number 13. I took the sprite and cloned it. Deleted all the frames in front of the diamond to make it number 0. Same size (100x100 - scaled to 20% to make it 20x20) and placed it underneath. When it is frame 0,it doesn't artifact.

These frames are simple black lines drawn to make a diamond. Transparent background.

This is driving me crazy. I've seen it with other shapes that are not frame 0.

Any thoughts would help.