GET /xhr/source-lastmod/* request throws "500: Something went wrong" (BB-10030)

I uploaded a pretty big git repository (OK it's git's own repository) and noticed that the commit messages weren't showing up in the directory listing. I used my browser's network profiler and noticed it was failing on this URL:

https://bitbucket.org/xhr/source-lastmod/OEP/git/0d6cf2471f426dd2b742e2285aad78381738be96/

When visiting the page, it gave me a code:

b6ebc71d6c1e4d27a534295247bfe056