I can reproduce it here, at first i thought that the pictures are not pixel-perfect identical, so i saved 4 pictures from capx above to my desktop, started a new project, created 4 sprites (0, 2, 3 ,4) and 1 sprite with 4 images(5), load pictures from my desktop there (to be sure that sprite5 and others have identical images) and i have the same result after export, but i can reproduce it only if i "Import frames - From Files" to sprite5, if i create 4 empty frames in sprite5 and then "Load an image from a file" for each frame, everythings is exported right! This sounds like i lost my mind so heres the .capx
Here i import frames to sprite5 and the bug appears
[attachment=1:1estfoy2][/attachment:1estfoy2]
Here i "Load an image from a file(folder icon in the editor and open the picture)" and everything exports fine
[attachment=0:1estfoy2][/attachment:1estfoy2]