We have a Jenkins node configured with an environment variable (MAVEN_OPTS).

Everytime we set this node offline temporarily (using the markOffline function in Jenkins UI), and then restart the machines, after the restart, the environment variable is still there, but the value is empty. I'm not sure if it's the slave or the server reboot which is causing the issue, I can try to find out if it helps.

Configuration History plugin shows that there is an Entry with source SYSTEM, which contains two Changes - the marking as offline (<temporaryOfflineCause class="hudson.slaves.OfflineCause$UserCause">), and the removal of this ENV value. If I don't restart while the node is set to offline, there is no issue. If I set it back online, then restart, there is no issue either.

Please let me know what else information you need, it's probably a complex to follow issue.

The false behavior started after the last update of jenkins core and our plugins. It's been correct before. It's less than two weeks old.