One of our newer machines was mistakenly downgraded using a 10.12.6 base image made by AutoDMG. This replaced the Recovery_HD partition and the machine would not boot into recovery mode or into Internet recovery mode.
The recovery partition is being replaced and it is not easily accessible. There are all kinds of security workings in the APFS recovery partitions so the issue is more than likely the internet boot trying to leverage some of those working or it's something as simple as being a different file system.
When you try to boot it goes immediately to internet recovery mode. If you try to option boot you see a 10.12 recovery partition but when selected it takes you right to internet recovery mode again. After either picking a Wifi network or having a USB-C network adapter plugged in the computer would show one of two things. A spinning globe with a blank black screen or the spinning globe with the "starting internet recovery this may take a while" The computer was left to sit overnight and multiple long duration attempts were made on different networks to to see if it was a network issue or download issue.
The fix is as follows:
1. Put the machine in target mode.
2. Connect the Disk to another machine running 10.12 or higher
3. In Disk Utility.app erase or partition the disk
4. Make sure it is set to GUID the partition option
5. Give it a unique name (important for step seven later as it is easier to find the drive in the list)
6 In terminal
sudo diskutil list
7. Take down the disk identifier /dev/diskN for the uniquely named drive’s . There is a number in place of the N
something like /dev/disk2 or /dev/disk3 It all depends on how it shows up in the list with the unique name.
8. Double check you did step four and five correctly.
9. There will be a sub disk identifier for the mounted drive /dev/diskNsN. Again there are numbers in place of the N. Notate it for the next step to make sure it is for the drive you have connected externally with the unique name.
10. Run the following command to unmount the drive using the sub disk identifier.
sudo diskutil unmount /dev/diskNsN
11. Run the really destructive command (where N in /dev/diskN is the number you took down in step seven)
sudo gpt destroy /dev/diskN
12. Booting into recovery mode will now work
