This sounds like a Red Hat issue: https://access.redhat.com/solutions/4973191
Are you doing a software install of QRadar (using your own hardware)? And what Red Hat version are you using?
I think if you are seeing install errors due to a grub.conf issue or something not updating as expected when installing QRadar, you should open a case so support can review the error. I do not see this error specifically logged in our defect system, so you might want to discuss this issue with us so we can review in a case.
#QRadar#Support#SupportMigration