Blender Version
Broken: 15acbbdc1ec

Short description of error
When baking I've encountered this bug a couple of times where black stripes appear in the baked image. Their size and distance is determined by the tile size in Properties Panel -> Render -> Performance -> Tiles.
When the tile size exceeds or matches the image size then the lower third of the image will be black.
Here's an example file. Just bake the current settings.