vertical navigation accuracy

I would like to ask, when I sometimes fly the same route and turn on VNAV, why can an aircraft with autothrottle accurately guide the aircraft to land, but something like the Q400 cannot land well on the runway in the end?

When flying DASH8-400, using vertical navigation, there are two situations: either you can land on the runway accurately, or you can land like the first picture, and the errors are almost the same. Is it an error in the system algorithm?

Quote from Jet-Pack (IPACS)

Is this issue isolated to the Q400 or are other aircraft affected too on this particular runway?

Unfortunately I don't have full control over what the route spits out, so I can't debug this. It might be an airport elevation error, perhaps the designers entered a wrong elevation for the airport? Then it should be an issue in all aircraft.

I feel it should be a problem with the aircraft, because the crj900 will also have this problem, and there are also aircraft with auto-throttle, but the chance is very small!

Quote from Jet-Pack (IPACS)

Is this issue isolated to the Q400 or are other aircraft affected too on this particular runway?

Unfortunately I don't have full control over what the route spits out, so I can't debug this. It might be an airport elevation error, perhaps the designers entered a wrong elevation for the airport? Then it should be an issue in all aircraft.

I carefully observed the vertical profile of the aircraft with autothrottle. One mile corresponds to about 300 feet high, and the one shown in Figure 1 is much lower than 300 feet.