If you click the back button on any screen where the installer has started a background task, the task continues while the UI goes to previous screen. When background task finishes, the UI jumps forward by itself to whichever UI would have been next from the screen where back button was pressed. If you go forward + back + forward to start the background tasks multiple times, the installer either crashes or gives various errors.

If back is disabled, at least stopping would be nice to have feature. For example, when installer starts to download and install gigabytes of data, a way to stop it would be nice.