I have around a dozen job generator jobs started by a starter job. All of these job generator jobs have the custom workspace directory set with multiple variables inside (taken from the starter job), and these get expanded well in the generated jobs.
Something happens after a few invocations, and the generated jobs don't get the custom workspace setting. This causes build FAILURE, and when I check the reason, I usually find that the custom workspace setting has disappeared from the generator jobs. Sometimes reloading the configuration from disk works, but sometimes the setting disappears first from the config.xml files while still showing up in the job generator configuration page. The change occurs in every generator job started by the starter job.

Other configuration options seem unaffected.

Version: 1.22 (had the same issue with 1.20)