Parent link broken for Site admins using Group Content Menu

Problem/Motivation

When adding a new link to a group content menu as a Site Administrator role (also group admin) the parent link dropdown on the add link page defaults to User account menu (and includes every menu on the site except the current one) instead of the menu in the URL.

When doing the same as a group admin or editor without site admin it works correctly.

I have narrowed it down to V3 of this module and am attempting a patch to allow Site admins access in MenuParentFormSelectorDecorator.php.

GCM 1.x is not supported but I am in the process of migrating and maybe this could affect other modules as well? Or I could be way off haha

Steps to reproduce

This is a large custom site but I believe the conflict is between Simple Menu Permissions 3.x and Group Content Menu 1.x.

Proposed resolution

Patch (so far not working)

Remaining tasks

Is this a viable way forward or is something else better?

User interface changes

API changes

Data model changes