Wow, this took a long time to identify what causes the issue. We have a Web Hook that post changes (Library Updates, File Version Updates) on all of our Shared Library files in slack. However, it appears that some of the files do not post anymore. It turns out several of us started using branches for iterating and once a branch is created the file no longer triggers web hook events. The worst part is it is not only if it has a branch but IF IT EVER HAD ONE. Even if you Archive > Delete all branches it will never trigger a webhook again.
So far I have tested this with
LIBRARY_PUBLISH. I am hoping this is a quick fix as it is now impossible for those libraries to post changes in Slack anymore which is what our devs use to implement the changes from the design system.