Columbus Head Unit Restarting Continuously (2014 Yeti 5L 4x4 TDI)

First up, I have spent quite a lot of hours researching here and at other places about this issue, but would welcome a response that shows I'm an idiot by leading me to an easily found answer.......

I believe I have a relatively common issue with what I believe to be the Columbus head unit in my 2014 Yeti 4x4 TDI. Many months ago it started restarting now and then, but generally working normally. This has developed to a continual restart loop that very occasionally starts playing what I was last able to set (radio, my phone playlist, etc.). It is now at the point where it is more or less impossible to access the system functions (Setup, etc.).

The following may be relevant:

1 - I have a rear parking sensor problem that predates the radio problem. Sensor short circuit I believe. Alarms when in reverse. It had worked for a few years beforehand

2 - I replaced the battery after the radio problem started, but not to try and fix it (It wouldn't start after a couple of weeks without running)

What I have done:

1 - 'Soft' reset (switched car on/off)

2 - 'hard' reset (Seem to be '<'+'>'+'mic' on mine, but also tried holding in power button for 30s, 'Eject'+'mic'+'setup', and done all of these 5 times)

3 - The battery has been disconnected for at least several hours on several occasions

4 - Removed the unit and checked for dirty/loose/damaged pins, connections and connectors

None of these made any noticeable difference

I think I probably have an internal power issue in the unit, but this seems to be more associated with the Bolero unit, which leads me away from that.... Before I look at replacements I would like to confirm it really is done for.

I would like to try updating the software and firmware, but the info online seems to be centred around RNS-510, which I cannot link to my unit in any way. All of the Yeti-related .iso disk creation procedures from back when the car was new-ish seem to have dead links, and I have no idea what FW and/or SW I should be updating it to anyway.....

Details from the various head unit stickers below. Any help from anyone would be much appreciated.

• Stamped in main case:

  • SKZ6Z7N6327037

  • 40352476 001

• Big Label (Class 1 Laser Product):

  • Manufactured November 2013

  • BS0013476327037

  • A2C91598300

• Label next to pinout label:

  • 3TO 035 686 H

  • HW: H21

  • SW: 6270

  • *014SKZ6Z7N6327037F*

  • 000532850

  • Continental

  • A2C91598300

  • VD1 

  • Radio Navigation

  • B 23.11.2013

  • Made in Czech Republic

• Label on bottom of facia:

  • A2C89702900

  • 131004-447372

  • Operator: 018

Ed