It's a 2D character. I've just had a play with the deceleration value, and even reducing it to 1, the frame of idle is still visible. Face after move is not checked.
I see the same issue if I ask the player to follow a path - he'll walk from the cur…
Thanks for the thoughtful reply Chris.
So far I've gotten by without having to overcome the navmesh issues, just by luck of having a bit of wiggle room in the art - but the tip for using a Cutscene and controlling the active navmesh is a good one.