I get this weird elevation bounce when I land on certain runways in FSX.  I want to say about 65% of the time this happens. It seems its not specific to the pmdg 777 but since that's all I fly, its hard to say how often other aircraft do it. Here's a video I made. 

 

 

 

 

 

I get a similar problem at certain airports. I believe the AFCAD for an airport defines what type of surface the sim thinks you are on at any given point, I believe the bouncing indicates that you are not on a paved surface. I found that from the UK2000 forum as I have a problem with the bouncing a one of their airports.

 

Have you noticed if it's specific to certain airports?

it's not PMDG 777 specific, it's airport specific. I have that on certain airports, and it can be reproduced every time. Interesting thing is that is seems to happens with some very best flight models for FSX - Maddog, 777, MD11

 

I have no idea why this happens, my only "fix" for this is to imagine there are just some sloped and bad mainteined runways...  :lol:

p.s. I'm not sure about runway type theory, for me it's happens every time on the same place on runway, and it bounces just one time

Try setting your mesh complexity a little lower - to say 75% and see what happens.. fixed issues for me with others bouncing