Most of the times it's BCU settings get somehow "disturbed".
When i switced from sls to coils and then back to sls,i also "lost" TC dashboard light although i didn't change such a setting.
Last week i was looking a friends Disco 2 with a nanocom.
The interior lights were going off at 15 seconds after i opened a door,not 10 minutes after as rave states,after much searching i found out tha BCU was set at transit mode .
I know this Disco for 2 years and all we've done was to set the sls heights and clear some sls faults sometime last year,so from times to times the BCU settings need some "attention"
Cheers.