Update the firmware of Hantek2D72/2D42/2C72/2C42

TKI

Hello, I'm hoping this is the right place to ask. I purchased a Hantek 2D72 a few months ago, and today it was having issues - trying to adjust the view of a triggered captured waveform would reset it to a different invalid waveform, or simply do nothing. So I attempted to update the firmware via the Hantek application software (May 2020 version) and bricked the scope (bad state machine in firmware) during the erasure step.

I attempted the "rescue" mode from the same update tool: battery removal, hold F1, connect USB, attempt to update with Rescue ticked - same error.
I attempted the alternative method with dfusedemo and 2020-07-27 firmware DFU, this resulted in the same error and the scope being unable to power up at all, power button unresponsive, holding F1 to trigger DFU mode at power up was also unresponsive (no lights or flashing buttons)
I followed this process to connect to the TTL debug port: https://www.youtube.com/watch?v=-uF2fdVxx1E, which successfully reloaded a bootloader. I was able to use F1 to trigger DFU mode again, but another attempt at a full firmware update in dfuse made it through erasure, and failed (bad state machine in firmware) at 2% uploading the firmware image.
I re-uploaded the bootloader via TTL again, and tried via the Hantek2000Update software again, same result.
Out of curiosity, I managed to track down a complete 512KB firmware dump from another 2D72 to try via the debug port, but it is from April 2019, my unit's original firmware was August 2019, the device boots with an upside-down display and inverted colours. Attempting a firmware update from there still resulted in a "bad state machine in firmware" following erasure and a bricked device.

The rear PCB shows the markings "HT2xxx_M", Rev.A09 2018.11.
The front PCB (with the user controls) shows the markings "HT2xxx_KB", 2018.11 Rev9

Is there a current bootloader for this hardware revision I can use to update to the latest firmware, or at least recover the firmware that was on there previously?
Is there a different process to recover the firmware for this device?

Cheers.