Unable to boot PI3B from external USB HD anymore

Start by reproducing both boot scenarios with the September 2019 Raspbian Lite image, the config.txt setting, and the SD card cmdline.txt change described in the report. Compare the available output with the attached screenshot and linked linux#3126, while collecting the missing raspinfo, firmware, OS, and kernel details. Done means identifying a reproducible kernel-related cause or confirming that the system boots from the external USB drive.

Is this the right place for my bug report?
An issue with booting the PI from an external USB -- this used to work. Bootloader comes up (sometimes), but the kernel won't finish loading.

Describe the bug
General boot failure when attempting to boot using an external USB Drive.

To reproduce
Two scenarios:

1. External USB HD Only:

• Image an SD Card with https://downloads.raspberrypi.org/raspbian_lite_latest (version September 2019 - full version archived at https://downloads.raspberrypi.org/raspbian/images/raspbian-2019-09-30/2019-09-26-raspbian-buster.zip)
• Set config.txt setting program_usb_boot_mode=1
• Boot PI (it works)
• Powerdown PI
• Image external HD.
• Set config.txt setting program_usb_boot_mode=1
• Plug HD into powered usb hub, plug Hub into PI
• Boot PI.

2. Boot on SD card, rootfs on External HD

• Set config.txt setting program_usb_boot_mode=1
• Boot PI (it works)
• Powerdown PI
• Image external HD.
• update cmdline.txt file on SD card to load from root partition on external HD. (Note: balenaEtcher may set Disk UUIDs/PartitionUUIDs to the same value -- be sure to check and modify if required!)
• Insert SD & plug in External USB HD.
• Boot PI.

Expected behaviour
System boots

Actual behaviour

1. First boot gets four Raspi's. Second boot, no splash or Raspi's. See https://github.com/raspberrypi/linux/issues/3126
2. See attached Screen

System
Copy and paste the results of the raspinfo command in to this section. Alternatively, copy and paste a pastebin link, or add answers to the following questions:

• Which model of Raspberry Pi? e.g. Pi3B+, PiZeroW
• Which OS and version (cat /etc/rpi-issue)?
• Which firmware version (vcgencmd version)?
• Which kernel version (uname -a)?

Logs
See screenshot of available output (Scenario 2)

Additional context
None currently available.