Applied Updates and Experienced Boot Problems

So yesterday, myself and colleague installed updates on our Zorin workstations at two different locations, which included updates to the kernal and grub boot loader, both workstations were temporarily bricked - classic black srceen "no boot device found, press any key to continue" style.

The two workstations are of very different build-types / hardware, started like I think with two different versions of Zorin I believe.

One workstation was much harder to recover because we were locked out of the BIOS and one-time boot menus, so that needed the system dismantelling to remove the CMOS battery and reset the BIOS to get in.

I've been using Zorin a year or two now and haven't experienced this before. I have some more workstations which I look after which have similar updates waiting, but this makes me reluctant to apply the updates now.

Has anyone else here experienced this with updates very recently?

Sorry I should add, we were locked out at the point of reboot. It is as though something automatically triggered the BIOS into selecting a non-bootable drive. Both systems had more than one drive installed but there were no removable drives like USB / external drives attached at the time.