Characters are not able to use tall structures, at a certain elevation they are forced into a freefall animation.
Last patch slightly changed this, character now insta-dies when it's forced into said animation.
This is a true game breaker as our mod (2017 mod) is using very tall structures, or at least we would like to.
http://i.imgur.com/xBuAfkG.jpg
http://i.imgur.com/qVlihRQ.jpg