Just been reading that a loose tailgate latch might cause the ff to think the tailgate is open. The r/h catch on the lower tailgate on mine has some play - not a lot, but is not as 'solid' as the l/h - when closed. Could this have led to a battery drain I experienced last week? QUID FACIUM TIBI
ANTEQUAM ALIIS

2003 TD6 VOGUE Zambezi Silver
tows 2006 Lunar Delta 540/2

I wouldn't think so, my lower right hand catch didn't work until I stripped it and cleaned it but I didn't get the tailgate open warning. If you don't get a tailgate open warning when driving I wouldn't think it would cause battery drain.
Depending on the year, headlight wipers not parking, final stage resistor, weak alternator, water ingress into rear left quarter, or bad earth or connection are more likely causes of battery drain .