Strange one for you:
Third brake light was only working 50% of the LED’s plus, while switched off & locked up in pitch dark, you could see a slight glow from the 50% working LED’s.
Changed the unit for a genuine LR one, all working brilliantly…….but…..again when shut down & in the dark, there’s a very dim glow from all of the LED’s. You have to get close to see it, it’s not blatant but it’s there.

Any ideas? 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

Try checking again 30 minutes or so after the car is locked and fully "gone to sleep" - my L322 used to do that.

I'll try that tonight although I'm pretty sure it was 'hours' after I'd looked her away.

There's two earth points on the hatch, I'm wondering if that could be an issue although everything works fine. 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

replace whole lamp.

I did! 😂
Brand new genuine LR one, just short of £140. 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

An LCM fault usually sir…

I could do with a little more help if you don't mind.
I've googled/forum searched for LCM issues & mostly they relate to the older L322 [mine is the last of the L322's] & usually are associated with brake lights [x2] on when the car is locked etc. Mine is purely the third brake light.
I can't find anything that points to just the third brake light.
You know more about these girls than I'll ever do, so if you say a new LCM will fix it, I'll go with that.
One assumes there's just the one LCM [near drivers footwell?].

Appreciate any help you can give. 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

Probably start with checking connections or any sign of dampness first, rather than just changing it. You never know, might be an easy fix….

 2011 Range Rover Vogue SE 4.4 TDV8

Previous cars :
2003 Range Rover Vogue TD6
1999 Discovery Td5 ES
1995 BMW M5 3.8 6 speed
1992 Range Rover 3.9 Efi Vogue
1992 BMW M5 3.8
1988 BMW 735i SE
1989 Ford Sierra XR4x4 2.9i
1981 Ford Fiesta Supersport

As above, check for dampness, unplug the LCM before locking and checking if the brake light still stays illuminated. Check for continuity of wiring from the LCM to the third brake light. All standard stuff sir…

Currently not advising you change the LCM without proving the above first sir…

Craig 👍

Thanks awfully 😁 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC

I have the same issue but only the middle 2 leds are glowing:

Double check that you’ve only got two when the brake light is on……… 2012 Orkney Grey Westminster 4.4TDV8 with Ivory interior.........nice!
BMW R1200GS
Alfa Romeo Giulietta
Just one Montesa now, 349 White Wonder
Austin A40 Farina MK2
1975 Morris Marina 1.8TC