I tried to rename a job in Hudson. This resulted in copying only parts of the
job folder to the new one, e.g. not config.xml.

Superficially, Hudson behaves as if it worked OK.

But if a new job with the old name is created, the original config.xml is
overwritten and lost.

Why not just rename the job folder?

Another related problem is that the GUI freezes for several minutes after
confirming the rename (while apparently frantically copying), and the user has
no idea what is happening. (Hudson doesn't respond to other browser clients,
either.) It would be better to show at least an hourglass or so.