The first thing I’d try would be to open each duplicated widget blueprint, hit Compile and save it. See if that helps.
edit: Also, it seems that in your Main Menu, you have the reference variable to the Dev Menu → select that var and toggle the Instance Editable checkbox.
Hello! I create at the moment my option menu and i duplicated the first option menu and create with it the dev menu.
I duplicated nearly all menus from each other and i havent errors before…
I dont understand what the error really mean because its all like the other menus and they work :o
"Fast CreateWidget Warning! This class can not be created using the fast path, because the property DevMenu on W_SGT_OptionsMenu_C references DevMenu. Please add “Instanced” Flag to this property".
Can someone help me? 
