Did you import File > Scripts > New Comp From Character Animator Recording.jsx?
That solved the issue, thanks!
And even better - AE dynamic link is coming in next release.
The sequence is static when I put the precomp into a scene, it works fine when I go into the composition but it doesn't play when put into another one.
And if I put that scene into another composition, the PNG sequence disappears entirely.
EDIT: Solved, it was just placed in a random spot in the composition when I added it in.