sequencer uv render issue

Hi
I’ve got a texture that i’m moving uvs to animate a 2d mouth, I’ve set up a bone that moves the required coordinates in maya eg x,y which i use to move UVs un ue4 via a blueprint and dynamic material instance.
I’m animating the mouth shape to change over 1 frame and all seems to work in the editor fine but when i render out from sequencer the uv mouth shape change is animating over 3 frames and the middle frame shows the Uvs midway between the keyed mouth shapes.

276523-render-issue.jpg