This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.
A user on the AnswerHub pointed out that his reflections when using a Movable Skylight with Distance Field Ambient Occlusion produces black results when combined with a reflective material.
I traced this issue all the way back to 4.9.2, and it exists there as well. I spoke with Tim Hobson and we came to the conclusion that entering a bug would be the safer choice, as I am unsure whether or not this is a limitation, a bug, or expected.
Note I can reduce the severity of this issue by modifying the Min Occlusion and Max Occlusion Distance values on the Skylight, which I can pass on to the user.
Download and Open attached project.
Head over to the existingAnswerHub thread and let us know what's up.