Roto Brush 3.0 not propagating, but 2.0 does.

Hi, 

I'm using AE on a PC. When I use Roto Brush 3.0 and mask a person with say a white background the mask only lasts for 2 frames before selecting the whole screen. When I change the selection to Roto Brush 2.0, it renders properly. I've tried multiple videos. I've tried reinstalling. But I still get this issue which means I can't use roto brush 3.0. 

Are there any suggestions to fix this?

Thanks, 

Dom