Assign CI runner to project

I was working on a GUI tool that helps us to manage our runners and projects because our Gitlab instance has about 600 users and 400 projects, so creating shared runners is not good idea since then would be hammered with work for other projects. We are currently locking all our runners (about 15) and as admins assign them to our projects (about 100)… new projects and new runners is pain.

I am currently having issue that I am not able to send Gitlab API request that assigns locked runner to a project, even if executed from admin account. I was trying my luck with “GET /projects/:id/runners” message but this responds that runner I supplied is locked.

Any Ideas on how to get around it?