Power tailgate closes fine but won't open
 

Here's the latest:
My set up allows for three methods of opening the power tailgate:
1) use the button on FOB
2) Slightly lift the hatch handle
3) Use button on console

At this point if I try any of the above methods, the hatch starts making the usual noise, lifts ever so slightly (mm's), gives up and returns to its resting position.

If instead, I use the hatch handle and help it get going through the first six inches of upward movement it then continues without issue. Button works fine to close.

Any suggestions?

I know there will be an anti-trap sensor to stop it closing on people (though it's whacked me in the shoulder without stopping before - ouch!). I wonder if there is similar on the opening to prevent it getting damaged if inadvertently opened in a confined environment. Perhaps this is being activated somehow?

Or it could be a sign of a falling opening mechanism.

Yeah, I'm thinking that it's the latter but was hoping to get a confirmation of what part is the problem. The motor and hydraulic cylinder are not cheap! As the parts guy at the dealership said, it's not cheap to have the tailgate do what you could arguably do yourself for free!