Unable to Install Big Sur from Recovery?

I've wiped the drive on an iMac Pro I'm working on, and haven't been able to reinstall the OS from recovery. Each time that I try re-installing, it'll proceed until ~75% complete and then pop up with the error "An error occurred installing macOS. You can try again to complete the installation."

I've tried booting into Recovery with Command+R, Command+Option+R, and Command+Option+Shift+R and formatted the drive as APFS each time and tried installing. All end up with the same error.

I tried creating a bootable USB with Big Sur but got an error from that as well (although different, I don't have the message for that one but can run through it again if need-be).

I'm also unable to install Catalina from USB as I have to adjust Security settings from Recovery. However, I need an administrator account on the device to do so. The problem with that, again, is that I have already wiped the drive and the admin account is no more.

I've never had a Mac be so temperamental! Does anyone have any advice on what steps to take next, or is my best bet just to try to bring in this gigantic 27" iMac into an Apple Store and have it serviced?

Thanks in advance for any replies!