ATM, ULandscapeHeighfieldCollisionComponent's scene proxy is created all the time, although it's only used for displaying collisions when Collisions mode is on. The scene proxies pre-allocate a very large vertex buffer to do so, which is by and large redundant data with the ULandscapeHeighfieldCollisionComponent's data and is only needed for debug display.
For very large landscape, it can be both a performance and a memory problem issue since we regenerate the scene proxies any time a CVar changes.
We need to :
[Link Removed]case where this was reported
Load a map with a large landscape
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-169387 in the post.