Grub /boot issues linux server

We are urgently looking for very good system admins with many years experience handling linux servers to solve a boot issue where installing Grub is corrupted. A very good Freelancer has been working on it already but even with his very high score and good skills he hasnt been abkle yet to get it done. So, please do not react if you are not very good in solving these kind of things as you need to work with the freelancer who works on it now and he has done already the basic things. So we need someone who can help him.

Server is linux/ubuntu and openstack