Well, OPERATOR ERROR, and then some.....
We had just dug a wildlife pond and I couldn't resist a trip over the spoil sand bank.
So our T6: Just a 20mm drop
Slightly over sized 235/60/17 M&S tyres
4mo. with Rear Diff locker & DSG
And what I did wrong........didn't turn off the Traction Control, so as soon as some of the wheels lost traction, the engine revs dipped, and It was a disaster in seconds.
After being pulled out by our Navara;
I tried it again with traction control turned off.... completely different outcome no problem.
And the lessons were, when driving on loose sand:
Lock the dsg box into gear 1
Engage the rear diff lock, if you have one, and its not too twisty with a too higher grip surface.
Dis-engage Traction Control - it kills your engine revs and you instantly loose torque & momentum, within a couple of weak wheel spins on loose sand, holes are dug and you are going no-where. If traction control just braked the spinning wheel(s) (which EDL-electronic diff lock does) that would be fine, but it doesn't it kills revs, and that is a big issue in my experience.
Lower tyre pressure from 40psi (ish) to 16psi (ish)
Oh and have a Navara (now an Amarok) handy to pull you out, as they are about a 1000% better off-road with the right tyres, than a T6.