When using the Artifact Resolver build step, there are two configuration options to set the update policy for snapshots and releases. If you select a different policy and save the project, the configuration is saved. But the next time you try to edit the project configuration the values are not read correctly from the saved configuration file. Instead they are reset to their default values. So if someone just opens the project configuration without changing anything, and saves the project, then the configuration on disk will have changed by resetting the update policy settings to their default values.
I've had a look at the code, but haven't been able to create a fix. The configuration options in the jelly file are data backed, so the values are read from a data source. However the drop-downs always selects the first item in the list when loading a configuration from disk. This would need to be changed so that they select the value from the configuration file.
There are several other issues in JIRA that could be triggered by this bug.