Pretty annoying but here is the fix, all credits to https://github.com/vdemedes

Node 5.x
http://blog.z-proj.com/running-ghost-with-node-v5/

Github issue
https://github.com/TryGhost/Ghost/issues/5821

remember to backup first
https://www.allaboutghost.com/how-to-backup-your-ghost-blog/