Hey Mo
If you alternator is charging fine then I would suspect a fault the Battery Monitoring Support.
If you look at the negative battery terminal, there will be a connector with 2 pins. 1 signal and 1 positive.
You will need to do wiring checks to make sure there isn’t an open circuit anywhere along the wiring.
The positive travels from the positive terminal and go to the BMS.
The signal wire (Lin Bus) travels from the BMS to the Body Control Module in the passenger footwell.
I would suspect the Lin Bus wire may be at fault as I have come across this before.