Summary

When user view a PR, Bitbucket Page prompted an error saying:
"We failed to load the JS word differ. Try reloading in a few moments."

Output from browser console:

#!python
Uncaught (in promise) Error
    at new t (pullrequests.js:1676)
    at wait-for-global.js?7ada:31

Investigation done

1. Issue persists on different browsers
2. Only happen on certain PRs
3. Disabled browser Add-ons