Linux guest won't boot unless hard disk is set as the priority

[Rusty_Almighty]

After installing the latest CentOS 7.8 The OS refuses to boot unless the boot order for the VM is specifically changed so that the VM boots from the disk first. If I set the boot order to something else (for example network for IPXE testing),the operating system instead shows an error "fatal: int18: BOOT FAILURE". Most of what I found online talks about installing the disk in GPT vs MBR, but that shouldn't have much bearing since I know I installed the VM as MBR. None the less, I still tried to change the VM to UEFI since that is what the online community instructs. However, no effect was detected besides the VM booting into the UEFI shell. However, if the boot order for the VM is changed, even though the other boot options are not being used and the option for disk is eventually reached, the boot option for the disk will eventually show the error.

[Rusty_Almighty]

Error as shown from virtual box guest OS console

[Rusty_Almighty]

In addendum. If you put the boot order to boot off of the disk first, then the OS boots up as expected. I've also confirmed that this doesn't appear to be an issue in VirtualBox 6.1.20.

[janitor]

We cannot even begin to guess what might be wrong without log files from the VM, ideally for both working and non-working scenarios.