Don't they use radar altimeters to get altitude? You don't need to rely only on image processing. You can even pull off stereo using a single camera since you are moving and know the altitude at every point.
https://en.wikipedia.org/wiki/Kalman_filter
For distance during landing I would be thinking a spatially maximally distributed array of quartz-shielded, thermally-supported laser TOF sensors along nominal extremities, but that's just because they're familiar to me, small, power-efficient, highly linear, relatively accurate, and cheap. Unsure if the IC physics assumptions work in non-atmospheric conditions. Perhaps the output can be re-scaled to obtain cheap and accurate enough readings.
A non-dilettante with an actual physics degree would clearly be desirable ;)
The second sounds like bad process leading to bad input, at which point it becomes garbage in, garbage out. The workaround was untested and insufficient.
While you are of course correct the filter will not fix these, none of these are the fault of the filter, they are all human process issues that are firmly out of scope.
This one seem to use scaled down Soyuz capsule as reentry vehicle. They must have reused a lot of proven hardware and software unlike those.
Apparently cameras also have issues because the lack of atmosphere means everything is high contrast.
So basically, you don't actually know your altitude, and your visual systems may not be reliable.