Full-width layout will not save

Following the instructions here:-
www.joomlack.fr/en/documentation/maximen...-a-fullwidth-submenu
I am trying to create a full-width mega menu.I see there are two options: 1. Transform all submenus in a fullwidth layout  or 2. Select which submenu to make fullwidth  but the menu was built with menu builder so I think option 1 is the only option available. Is this correct?

Using option 1, I try to go to  styles>layout>fullwidth but when i press save and then close and re-open it again, it has reverted to "Default".

Is this unexpected behaviour and what can i do to solve it?

Hi
if you use the menu builder, you can set the fullwidth option for each parent item, see the icon in the image
 

for the layout saving issue, does the save work with any other option ? or is the problem global for the module ?
Note that if you want to setup the fullwidth for each menu item separately, you must leave the layout on default. If you set the layout on fullwidth, then all submenus will be fullwidth automatically
CEd

The saving issue also applies to some of the other layouts, but not drop down nor joomla default.

I have logged in your website and went into the module ID 990, the layout is on "fullwidth"
I don't see the problem here

is it solved ?

Thank you very much for lookign and I am sorry for my slow reply. I have moved on from that problem.
I never did get the layout to save but somehow I have managed to get a full-wdth menu anyway
I will close this ticket now.