D4 tailgate sticking

I've had a 2012 Disco 4 for the last few months and have been gradually sorting various minor issues.

The tailgate release actuator had been a bit flaky for a while so I replaced it yesterday before it completely packed in.

It now works every single time and makes a much more satisfying clunk as it does so. But the upper portion seems to catch a little now as I lift it - as if the latch hasn't fully released.

It's thoroughly lubricated so I don't think that's the issue. Could it be as simple as adjusting the release cable length?

Apologies if this is a simple question but I want I want to know all my options before I risk my very limited skills causing real damage.

A simple fix... Trying to open from the keyfob seemed to reset something and now it opens fully from the handle every time.

I spoke too soon.

The slight catching thing recurred and a few days ago the tailgate fully stopped working again - but quickly reverted to the odd getting slightly stuck thing.

Given that I've already replaced the actuator, has anyone any tips for figuring this out? Could it be as simple as a tired battery or and adjustment to the cable itself?

The button under the rubber on the outside of the tailgate rots away, on my d3 this sort of made it half open sometimes.

Will check it out - many thanks.