It appears to be a collision problem. The wooden stairs are meant to go with segments from the WW2 pack. Especially, the Chateau. You are using the common ground segments and you can see that AIKO gets stuck in the "ground" at the top.
Use the sample fpm called
GS12-WaypointsMultilayer.fpm. It is in the Samples sub-folder. If this works then their is no bug with v119. And I can vouch that it works in both v119 and v120.
There is also a post in the v120 beta thread that concerns this issue.
You just have to work with it by trying various things.
THEORY - you know everything but nothing works. PRACTICE - when everything works but don't know why. For me, theory and practice are combined: nothing works and I don't know why.