The modifier input value for menu items is an int property, which is not
compatible with the enum property used in node group socket definitions for
menus. Wrapping a node group with a menu will try to assign the int value from
the modifier directly to the enum, which expects a string identifier.
To aquire the matching string identifier, use the UI properties in the modifier
RNA, which contain the complete enum item definition.
Pull Request: https://projects.blender.org/blender/blender/pulls/139074
5180930e0d