Why character fall down through landscape? Engine bug

I have created binoculars with spring arm of camera, but when I activate camera and move camera around in the world then my character falls down through landscape, how I can fix it? Please help me!

I am using ALS Community C++ and default binoculars from there, you can create blueprint of binoculars and create there spring arm with camera and activate it with blend. After moving mouse around my character fall down. I do nothing with positioning of character only camera on binoculars with spring arm.

Something pushing the character around..

Can someone from developers of unreal engine say what happens? How to solve this issue?

Can someone create project based on ALS Community C++ plugin and attach camera with spring arm on binoculars mesh object? After pressing right mouse for aiming do camera blend and move around camera staying on landscape which created with world partition.

Please help me, i cannot resolve this issue! Something with bug of engine!