Oh no, the parallel universes collided! Balance must be restored.
LOL - I actually saw something similar when I stress tested the generator with more than one server. It happened to me when I generated two or more sandboxes concurrently, and so the random seed number was similar in multiple servers, causing the generated content to be identical.
What I did not see is a different map though, so this is more interesting.
I suppose I can add some fuzziness to the seed number to alleviate this. Do you happen to have the URL from the generator page? (the URL should have all the generation parameters).