It did help, tremendously. I was still seeing the old version from the German article, but seeing what you did, I was able to figure out how and why. Apparently the German Wikipedia, on using a file from the Commons, doesn't simply link to the current version of the file like the English Wikipedia does - instead, it generates a time stamp, and displays the image as it was when the article was last edited, even if the image changes in the interim. (This can be seen by visiting the German Masyu article, clicking either image, then looking at the URL.) I can see the advantages of that, but the disadvantage is painfully clear. What I just did was "edit" the German article, changing a whole lot of nothing, and that fixed it by changing that time stamp.

I was stuck on the misconception that there were four files here - two English and two German - but that's not the case: the German article was referencing the same files the English article was ("File" and "Datei" must get translated automatically), just older versions of them. The counterintuitive step of a degenerate edit (no actual change) was the last piece of the puzzle.

I can't state enough how much your effort meant to me here. Thank you. - ZM