If the user moves the RecastNavMesh actor in the level, the navmesh will be offset each time they change a Display setting in the Details panel.
RESULT
The rendered navmesh moves in the level each time a setting is changed.
WORKAROUND
Rebuilding navig fixes this.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-57162 in the post.