When attempting to export pictures to an HD slideshow video, I noticed that it completely fails to even begin the export at either 720 or 1080. I am able to export at the lower quality settings, but the pictures are completely blurry. I read a post that having portrait oriented pictures in your slideshow is causing the problem. Sure enough, I create a slideshow 720 or 1080 video with only landscape photos and the export works fine. I then try to create a slideshow 720 or 1080 video with nothing but portrait, and it hangs. It did this is the version prior as well, as I was hoping the update would fix this.
Here are my System Settings:
Lightroom version: CC 2015.6.1 [ 1083169 ]License: Creative Cloud Operating system: Mac OS 10 Version: 10.11  Application architecture: x64 Logical processor count: 4 Processor speed: 3.1 GHz Built-in memory: 16,384.0 MB Real memory available to Lightroom: 16,384.0 MB Real memory used by Lightroom: 2,202.4 MB (13.4%) Virtual memory used by Lightroom: 2,687.0 MB Memory cache size: 1,375.9 MB Maximum thread count used by Camera Raw: 4 Camera Raw SIMD optimization: SSE2,AVX,AVX2 Displays: 1) 2560x1600