This one was in an experimental feature, as part of the extra testing process of making this into a stable feature, we run into a bug.
Here is the bug fix:
The code is meant to detect changes in a distributed environment and we checked the wrong location, meaning that we never actually did the check. In 99.999% of the time, this already happened, but it exposed us to some nasty race conditions.
This particular piece of code has been the subject to multiple code reviews, all of which never noticed the issue.