Stumbled on that issue too.
I work with a GitHub source that's supposed to detect all branches and no PRs.
The GitHub repo's hook is set to send the events `push, branch created, branch deleted` and delivers them properly.
The multi-branch pipeline job strikes out the branch I'm force-pushing to and does not build it.
The event is obviously received because the branch is stroked-out but i'd expect the branch to be built instead.
That's a shame in our workflow because rebases tend to happen and in this case, the commits are not built and the branch is not built again until someone triggers a scan manually which is not the point of automated testing :-S.
The plugin's version is 2.20, Jenkins version 2.138.1.
Anything you can do?
There is no option in "Scan Multibranch Pipeline Triggers" to enable Github triggers.
Configurations of jobs created for each branch do not have the "GitHub hook trigger for GITScm polling" option checked.