When upgrading from 1.444 to 1.450, configurations for build promotions were lost. I have the job config history plugin installed, and it shows that the deletions were done by "SYSTEM".

I have seen this previously with some email-ext configurations being deleted in the same way.

Upgrade process was: shutdown jenkins, upgrade core, start jenkins (promotions were gone at this time when examining through the UI, along with several jobs), update plugins , restart (missing jobs came back).

Promotion processes were still missing after the restart, and had to be restored from the Job Config History.