It seems that Adobe has fixed a bug I had been dealing with for over a year. Every time I exported files from CC2014 there were full-frame white flashes/flickers in the video. These artifacts were not present on the timeline - rendered or unrendered. I was pulling (the remainder) of my hair out. After upgrading to the 2015 version(s), this issue magically disappeared. I am now going back and re-exporting timelines in CC2015 to replace files where possible.