This seems to be a reoccurring issue that I have not found a permanent fix for. For some strange reason, when I build a new VM and install it with UEFI bootloader, the VM runs and reboots perfectly. However, whenever I upgrade FreeNAS, the VM fails to boot because bhyve loses the boot device config. I can manually enter the Boot Maintenance Manager and select to boot from the path and GRUB UEFI bootloader. However, reboots would get stuck at the same point and requiring manual intervention each time. I also tried to add a new boot options and change the boot order so that it is the first choice. However, that added config is also lost on reboots.