I have noticed the elevation rapidly changed after landing the 777.  It does this about half the runways (maybe even more) in FSX. I attached a video that shows it.

 

 

http://www.youtube.com/watch?v=4GSkT9Y_xx0&feature=youtu.be

 

 

I'm having something similar happen to me at the moment. I'm parked at the a gate at Miami Int'l in a non-PMDG aircraft. I'm just sitting there observing VATSIM communications. Every so often I see the scenery around me do the same bumping as you showed in your video. Or perhaps it's the AI airport vehicles themselves doing the up-and-down bumping. I can't quite tell.

 

I've typically only seen it happen when I switch airplanes while parked at a gate or runway. When the new plane is "plopped" in, everything bounces for a second or two. I've never seen it happen after the initial one. I've also never put myself at this particular airport. And it's my first time joining VATSIM. There are a few things to rule out still.

 

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Gerard Beekmans

Try reducing your terrain mesh slider.. should resolve it.

So which one is it? Mesh resolution? Mesh complexity? 

It happens to me too sometimes, but seems to me that's not a PMDG problem, but terrrain problems. Could be what John said

I have noticed the elevation rapidly changed after landing the 777.  It does this about half the runways (maybe even more) in FSX. I attached a video that shows it.

 

 

http://www.youtube.com/watch?v=4GSkT9Y_xx0&feature=youtu.be

If it's what I think it is, it's most likely the terrian type chosen for that runway.  If you have ADE or AFX, you can see and edit what the runway is made of.  Microsoft mistakenly set some runways to grass or gravel, when they should have been asphalt or concrete.  This can be fixed with the above mentioned tools. 

 

This may not be the case, just trying to offer a suggestion.

 

John

So which one is it? Mesh resolution? Mesh complexity? 

 

Mesh complexity..