Hum, guess I'm definitely exposing my lack of physics knowledge, but my understanding was that entropy is only guaranteed to increase or stay the same in any is

Hum, guess I'm definitely exposing my lack of physics knowledge, but my understanding was that entropy is only guaranteed to increase or stay the same in any isolated system. That the inequality is >= not >. If so while like this exact example might not work, there isn't anything clearly wrong with something that just has repetitive motion