I've upgraded Jenkins (to 2.127) and now the Build Triggers section is not showing up any more on the job configuration page. I also had to upgrade some Plugins but afaik the Build Triggers section is directly integrated into Jenkins, right? So I would at least expect to be able to schedule builds periodically which is not the case.
The downgrade does not work again below 2.121 because the format of some plugins changed and when doing so the jobs don't appear any more.
I can't find anything on the changelog nor the documentation about that. I've tested a bunch of different security settings with no success.