Yes, you've either a wiring issue to the RLM, or a faulty RLM. No point in replacing anything at this point

Now, it needs diagnosing for wiring issues (fuses/power/earth/CAN comms)
If the wiring all checks out OK, it's likely a faulty module

I guess it's got to be done, but I'm not looking forward to it. I've checked the fuses, and they're all working okay. The battery is reading 12.5/6 with up to 850 amp output, which I think means I can eliminate them as an issue. It's time to strip back where there was a leak and look for any breaks. If there's nothing obvious, I think a new RLCM is needed. I've heard they need to be reprogrammed. Do you have any information on that?