The lander crash could have just as easily been happened using 2 different metric units. It wasn't caused by improper conversion, it was caused by no conversion. Each part assumed the other was using the same unit.
Nobody uses anything but meters and seconds with metric in science. But even if - using 2 different metric units would give answers differing by a factor of 1000 - a little easier to notice than Pound vs Newton (1 to ~4.45).
Is that m/s, km/h or kmps?
Sure, now. It took the loss of the Mars Climate Orbiter to end the Imperial madness at NASA.
A lander is engineering and science, and I can guarantee you that there is a non-zero probability of one part of a system working in m/s and another in km/h — which would lead to the exact same error.