Yes, I've seen this happen and it really bothers me as well. I constantly keep getting comments / reviews claiming that the algorithm is clearly not picking the best one or that the fitness function has a problem but that isn't the case here. Otherwise, the creatures in the simulation scene would also stop and do nothing - but they don't. They continue to evolve like expected. This is definitely a bug with the "Best of Gen." scene and I currently have no idea why it's happening. I'll probably have to figure out a way to "look into" their brain and see why they aren't doing what they were doing before even though they have exactly the same chromosome.
A major problem with this is that I don't even know how to consistently reproduce this issue. As you might have noticed yourself this doesn't happen all the time - in fact it only rarely happens which makes debugging it a lot more difficult.
So if you, or really anybody, could help me figure out how to reproduce this bug, I'd be very grateful!
Thanks for starting this thread!