I could imagine such an error occurring once or twice, but on three frames in the same scene? I do not know much about the animation process used during the 80s; however, I have seen 2 different DVDs that showed it for the recent past.
Animation Runner Kuromi was about a girl who works for an anime company. I believe that it showed a guy inspecting the cels before they were used. Of course that in no way proves anything, because I certainly cannot say what methods they used in making the 80s series. But I have seen ep 053 goodbye 1963, & that had only a background artist & a foreground artist. If you look at the pics of Atom & Uranium being dressed for school (above), you will see that in that case, there was no third layer, as I explained in those posts.

However, granted that we are dealing with a different series, but still Tezuka himself was the boss. While making a quality product was important, economizing was also. I can cite many occasions in the 60s series, when the very same sequence was used repeatedly (see the post about the furnace). This was especailly true in scenes of crowds fleeing an alien invasion, or what have you.
Still, I say that the thing cannot be resolved without more evidence. It just seems unlikely that so many frames or cels would be affected. It might be intersting to look for other frames in other episodes in which a fore, middle, and background seem present, with middleground characters moving in it.
