A question on animated webp images

[carmen]

Hello!
I would dearly wish to know if webp, as image format, has any issue with animations over tansparent background when the frames overlap, or the trouble comes from Gimp.
Here I append two gif animations:
    , on transparent background, and
    with the alpha channel removed from each frame
Well, I can get the second one, exported from the same xcf file, in webp--but the first one comes out a mess--some frames merged toghether, and bits of black where there should be transparency...

Thanks!