Reported in this thread
This looks to be a machine specific issue. I'd like to get some testing on different video cards and see if we can track down which ones don't work correctly. The implementation of DFAO has changed significantly between 4.8 and 4.9 and if I know what video cards the new version doesn't work on, I might be able to fix it in time for 4.9 and avoid a big regression.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-19377 in the post.