Permission "Manage menus Create, update and delete menus" not working

I have the same problem with 3.0.5. My customer wants to have exactly one group menu per group and only admins should be allowed to create/delete groups and their related menus, but group members with specific group roles (group admin, group content manager) should be able to create/edit/delete group menu items.

Where are you getting this function in your patch?
$this->getManageMenusPermissions()

I don't see it included in your patch or on the 3.0.x codebase:
https://git.drupalcode.org/project/group_content_menu/-/blob/3.0.x/src/R...