Pull requests not loading all diffs (BB-4272)

When viewing large pull requests, after a certain point the file diffs are collapsed, and have a 'Click to load' link. These links do not always load, giving instead a js error of 'head is not defined' at line 1098 of https://dwz7u9t8u8usb.cloudfront.net/m/c4ab365c4bdd/bun/js/bundle.js

The files that fail to load seem to be consistent (but there isn't anything special about the diffs that I can identify), and this happens across browsers (tested in firefox and chrome).

Edit: This is for git repositories