Tailgate fully opens under power, then starts to drop a bit from fully open which causes it to shut under power. Sometimes it stays fully open - Very Annoying. Any ideas of the cause guys?

I donââ,¬â,,¢t really know anything about that model of car but I believe you can set the open angle of tailgate,it might be worth trying that before anything else just in case it has lost its settings and is throwing a wobbler.

Done that but still don't stay open :-[

The two rams are designed to open and close on motors within them and once power is stopped the ram shouldn't move as its resistance weighted. When it does move the controller interprets the movement as a person pulling down the tailgate and hence why it then sets off on a close cycle.

Unfortunately the rams are sealed so, assuming you dont have any extra weight on the lid like a bikerack or spoiler, your only real option is to replace one or both of them.  ???

Checking measuring blocks within VCDS should show you which one is triggering the close cycle. I'm not massively familiar with the Sharan variant but assuming it's like the Touareg they both have clock sensors.