Can't undock a particular port

[Wallace]

Ok, so here's the thingy in question:

On the left is part of my Mun base (just a cupola and hitchhiker on legs with a couple of solar panels) on the right is a fuel trailer (fueltank, 2 probe cores, wheels).

What i'm attempting to do is pass this widget (block of batteries and RTGs and a mechjeb) from the trailer to the base.

The pair of ports on the left will undock, leaving the widget with the trailer, but the pair on the right will not so I can't attach it to the base, when I click the button nothing happens.

The trailer had the widget passed to it in orbit so I know it's possible to pass the widget from one thing to another, also, I tried undocking the widget from the trailer so it just drops on the floor and that worked ok. I also tried it on a different building in the base and had the same problem.

Anyone have any ideas what the problem might be?

[blizzy78]

Can't Undock Bug, How To Fix

[Wallace]

Yay, just tried it and it worked thanks.