Error 500 , while executing API call to restore fork relationships between 2 projects that has forks

The API to create fork relationships (POST /api/v4/projects/:id/fork/:forked_from_id) fails with a 500 error when trying to create a fork between 2 projects that already have forks, even after fork relationships have been removed via the UI/API.

https://log.gprd.gitlab.net/app/r/s/57lxu

ActiveRecord::RecordNotSaved: Failed to remove the existing associated fork_network_member. The record failed to save after its foreign key was set to nil.