This must be a regression
1) new map with the floor, delete directional light, place point light so it affects the ground, make sure its set to stationary
2) build lighting
3) place a static mesh so it casts a shadow on the ground, and scale it down so it's pretty small. change to Movable. Move in and out and see that the shadow pops in and out.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-40873 in the post.