Can't change UI from Manifest

Hi all,

Just treated myself to a new Rasberry Pi 4 and the standard 7" screen.
I’ve installed the latest (3.512, 25th June 2023) Volumio: all went smoothly and it works well with headphones.
The display works fine. In the drag-down I see through system settings that UI is set as ‘manifest’.
There are two other options ‘contemporary’ & ‘classic’.
If I drag down to one of the other options and save, after the progress bar runs along the system the UI reverts to ‘manifest’.

What am I doing wrong?
Should this feature work or do I need to understand command line commands etc. to get it working?
Many thanks

it’s a bug, please try to press save keeping the selection on Manifest, then you should be able to change the UI