Failure is an option
Given the nature of these missions its got to be assumed that a perfect landing in exactly the right spot is going to be an outlier, something that's worth working towards and trying for but unlikely to happen. The design should accommodate this. It will mean that its going to have redundant payload (Murphy's Law being what it is, once you design the thing on the assumption that it could tip over it will always land upright) but that's the obstreperous nature of machines.