Invalid Tumbleweeds with the Ambush flag still lose bounce height over time

Adding the Ambush flag to tumbleweeds is supposed to make them move on level load and perpetually bounce all over the place. However, it only half works. Gradually, tumbleweeds lose height as they bounce, so after maybe twenty seconds, they're just rolling all over the place, which doesn't make sense.

They get 'kicked' again when they normally would stop. Looks a bit strange at times, yes, but that's how Jazz (?) chose to do it.