If the installer performs some actions with a ProcessPanel, there is a good chance that the installer cannot perform these actions again. There should be a way to disable the "Previous" button and never let the installer go back into the ProcessPanel if it has already been executed.
Processes are now started only if they haven't finished with success before. So if they ever finished with success, it's possible to go back to the ProcessPanel, but the processes wouldn't be startet again.