One way of working on reproducible builds is to look at packages which fail to build reproducibly on our continuous integration platform. Looking at the output of debbindiff often makes it possible to spot common problems.

Sometimes, issues are more singular. sources.debian.net and codesearch are amazing helps to skim over the source code trying to figure out what is happening.

When I started to work on reproducible builds for Debian a year and a half ago, I never thought it would be useful to find actual release critical bugs. Until I had a look at libical debbindiff output.

Can you understand the issue and how bad it is?

Answer is in bug #773916.