Original ticket raised: "Can't unrestrict this because of parent page settings, however parent page (online team>project delivery) isn't restricted. It was originally created in my personal space which is restrivted, but when moved it's somehow kept the permissions from my space."

Response: "Have looked into this, seems it's a bug on Atlassian's side, the page is still retaining parental page restrictions from previous parent page regardless of the fact that it now has a new unrestricted parent page.
Will raise issue with Atlassian."