[Closed] Thomson dropper oddness – any ideas?

First ride with a dropper post today – a Thomson Covert. Lovely smooth action (no, that's not a euphemism) but when I moved the post further up to get proper leg extension, the dropper bit wouldn't stay extended. Annoying.

Now, I read something about needing to make sure that the cable (outer and inner) was kept slack when you move the seatpost up, which makes sense. So I may just need to feed a little more cable into the seat tube. Is that anyone's else's experience?

Also, anyone had problems slipping down into the frame?