We have a specific workflow that enables us to discover that bug. However, it could and will probably happen to other people soon.
When running scm checkouts in parallels in a Jenkins file, the changes discovered are discovered for every git checkout that runs at the same time.
In our example, we run checkouts with 8 threads in parallel (background: https://roidelapluie.be/blog/2016/11/18/gitslave-jenkins/ ).
One change is displayed in 8 different repositories, the 8 repositories that are checked out at the same time.
The next checkouts do not contains the changes, so I guess it is kind of a global variable that is reset after the checkout.