Range rover classic 1991 interior lights not turning off

Got in my range rover this morning and found when I closed the door, after a while, the interior lights didnt switch off. Also I was driving the lights would flick on and off now and again.

Anyone no whats going on here? I think maybe the timer switch?

Upper tail gate.
As they rot they start to flex.
Interior light staying on is early sign they are about to give up, as the frame isn't pushing the interior lamp switch all the way down.
While driving bumps make the frame flex. So lamp will flicker on or off, depending on how loose it all is.
Temp fix is to look at the upper tail gate & try re-alighning & adjusting the catches.
Removing the lower seal...... normally bows out with rust under neath.... can help get it to latch better for a bit.
Some-times, if you have enough metal left in the frame, you can weld or rivit some plates on the corners.
Ultimately, you need a new one...... most 2nd hand are just as bad!