I have noticed from beginning a weird behaviour with the promoted builds plugin.
A job configuration can be made as long as there is no promoted builds plugin configured.
Any changes made after the plugin is active/configured will result in a "Error - Failed to create".

In newer Jenkins versions do the changes in the job config simply not take place. The config file is completely wrecked in case you use an older version of Jenkins.
The config files for the promote plugin remain intact. Rebuilding the job configuration and activating the promote plugin will not lead to a reuse of the old promote config files. The inteface behaves like it is first time you use it. Saving will then overwrite the old configuration.

Only ways to make changes later on are either to deactivate the promote plugin, make the changes and save and then rebuild the promote plugins configuration from scratch or by making the changes with an text editor and reload the jenkins configuration.

I have made some research and noticed that the content of text fields in the job configuration are terminated with a
This terminator is removed entirely after the promote plugin is active. I have no proof but I think this is somehow related. The terminator is present until the passage comes that configures the promote plugin. Everything past the passage is not terminated.

So in other words. Tasks have the terminator, build steps not