What version are you running?  2.5.3

What's the URL of the page containing the problem? /r/<id>/diff/2#index_header

What steps will reproduce the problem?

Click on a review request that has a diff many of the diff files will not render.
These same reviews look good in our 2.0.18 installation.


What is the expected output? What do you see instead? I expect to see a properly formatted diff file (see screenshot below to see what I actually see)

What operating system are you using? What browser?  This is not a browser issue, but the server is running on Centos 7 against MySQL

Please provide any additional information below.
I know that this code is actually failing in the migrate diff function.  It was kind of tricky to follow, but for some of these requests there are numerous FileDiff objects and some of them have a "need migration" flag, yet the migration fails.