The fitness criteria for the climbing seems to favor non-moving creatures way too much. Probably because since they're dropped onto a hill most of them will fall down, and the most "fit" creatures is those that just tense up completely and avoid falling. I once even noticed one actually started climbing up but it appeared not to be selected as the best of the generation and instead chose the one of the many who just froze completely.
Btw does it favor moving to up along the hill or simply getting higher? It appears to me it's that only maximum y height is rewarded rather than max diagonal movement; cause in one experiment it seemed the ones actually started to make progress using it's limbs to crawl were out competed by those who simply stretched up as tall as they could be straight up. So the next generations were just static creatures that balanced on their hind leg and occasionally tipping over backwards and nobdy even trying to go right. They probably moved their center of mass slightly higher but they were not really moving.
Maybe the hill is slightly too steep as well and with the non-deterministic physics any progress will be accidental and not really reproducible (especially since the most fit seems not to be the ones who actually move but those that stand still and just shake in the right direction.)
It would be nice if we could adjust the hill steepness and fitness criteria as well.