Unable to install Software Update Security Update 2019-002 10.13.6 on 15" mid-2012 MBP

I have tried at least 8 times to install the Security Update 2019-002 10.13.6 on my mid-2012 MBP.

On my first attempt I got an error message saying that the firmware could not be updated. I decided to reinstall High Sierra just in case there was some corruption in the system due to my migration to an SSD in my MBP

Each subsequent attempt to install the security update resulted in my system getting borked and upon restart I am unable to boot and have to reinstall High Sierra to get my computer working again.

I have tried doing the update in SAFE mode. I have eliminated other startup items. I have read all the previous threads on this and followed suggestions given in those other threads.

I have also called Apple Support and they walked me through steps to reinstall HIgh Sierra since the previous attempts to install the update borked my system. When the update would fail, I'd get one of several error messages. On one such attempt I got this error after the restart:

Unable to install on this system

apple.com/support -2105D

Apple Support suggested that this was a local network issue and that the download was failing or getting corrupted so they had me connect via Ethernet directly to my cable modem. That may have been part of the problem as far as reinstalling High Sierra using Internet Recovery, but it still did not allow me to install the security update.

Other times I would get a black screen with error code at the top left corner.

Error: 0xB000000000000003, Cannot Load 'EFI/Drivers/TestSupport.efi'

Status: 0x00000003

Apple talks about Apple Hardware Test and pushing D key while restarting. That results in Internet Recovery. I never saw any Apple Hardware Test, only Disk Utility. Running Disk Utility found no erros.

I tried downloading the standalone Security Update 2019-002 10.13.6 and after reinstalling High Sierra, tried updating that way. That failed as well. Running Disk Utility found no errors and the disk appears to be OK. By the way, I'm using a 1TB SSD in my MBP.

I've also used the Terminal command line to do the update. Failure.

So while I'm happy for those folks that have not had a problem installing the Security Update 2019-002, 10.13.6, I would like to suggest that there seems to be a problem with it, at least on certain vintages of MBP's.

I'll be calling Apple Support again.