When I move the gear shift on my 2000 P38 Auto into a gear, I have to move it back and forth slightly to select the gear and have the appropriate LED/ Lamp come on.
So, I put it in drive and it shows neutral, moving back and forth gets it in place.
It's a nightmare getting it into low range as it won't sit in neutral while the cogs engage.

Before I start to take it apart, is there an adjustment inside the gear shift unit or is it down by the auto box.

Could this be microswitches that need cleaning????

have a look at cable ,were outer is clamped (not come loose and slipping )and at adjuster were it connects to box lever , display can be adjusted by moving xyz switch on lever assembly (its on slotted holes )

Asd James said, there is an adjuster under the car. It's not very adjustable though. I had to fiddle with mine as I couldn't manually select Low Range 1st. Now it's a little bit iffy getting it into High Range Park.