The digital displays on modern cars are known to sometimes randomly fail for no apparent reason. Sometimes it’s the whole display that fritzes, other times just a smaller part of the display will disappear. Usually, replacing the LED module is the fix.

From memory, this model D-Max groups the fuel and temperature gauges, odometer and the gear position information into a small unit in the middle of the dash binnacle. Which means it might be a bit complicated re-connecting the temperature and fuel tank sensor units to the new module, as well as making sure the new odometer reads the correct mileage for the vehicle. An auto electrician should be able to handle it, though.

Technically, of course, any car without a working gear-position indicator is unroadworthy, so this needs to be fixed rather than ignored.

Sandy conditions are incredibly hard on every aspect of a four-wheel-drive. The sand itself constantly shifts under the tyres and clings to them as well, dragging them down and making the engine and transmission work very hard to maintain progress. You may have already noticed that you use a lot more fuel in sandy country and it’s all because you need to be constantly making more power to maintain speed than in normal conditions. Turbocharged engines and automatic transmissions, in particular, can get very hot very quickly in sand.

With that in mind, it’s very possible that something in the driveline got hot enough for the car’s computer to go into limp home mode to protect what ever was hot from damage. Limp home mode often involves limiting engine revs and turbo boost, both of which contribute to heat production. This would explain why the car would not climb a crest but came good after a break.

Problems like these are hard to diagnose remotely, as there's a lot going on in a modern gearbox. But, conventional wisdom suggests that a noise followed by a series of failures of the same component (the oil seal) means something inside is bent or damaged.

The noise is potentially being caused by something misaligned and rubbing or a damaged bearing, and the blown oil seal is the eventual result of the damage/swarf/heat/friction that results. The other possibility is that the rear gearbox seal is being destroyed from the other end of things, as in the tailshaft. A bent tailshaft could set up harmonics, friction or vibrations that could kill the seal, but you'd imagine there'd be a vibration through the whole vehicle at speed if this was the case.

Your vehicle is under warranty (six years of it from new) so make sure the dealer is aware of the problem and their obligation to fix it.