File with diffs showing blank in side by side diff viewer

Seems to happen occasionally in varying degrees:

Environment

• OSX El Capitan
• Safari 9.0
• Dell 4k display

STR

1. open pull request
2. select diff tab (side by side diff)
3. view a file (seems to happen more often on larger files)

Expected

• Should see diff

Actual

• Diff sometimes is entirely blank, or in this case, one file is blank. See screenshot.