TL;DR:
We always knew that at some point there may be a more serious bug in restic that warrants a broader announcement. This is the story of how a small improvement that makes the code even more conservative lead to a small error which then caused a couple of unintended consequences. In the end, under some specific circumstances restic wrote incomplete snapshots to the repository.
This is a companion discussion topic for the original entry at https://restic.github.io/blog/2017-07-25/please-upgrade-to-0.7.1