Problems with mesh distort

Just been messing with mesh distortion patches again, sometimes everything works fine, but after a while, I cant mess with anything that changes the number of vertices, if I change the resolution of the mesh for example, the output goes black, if I delete the shader and try and recreate another, nothing appears in the patch. The only solution is to shut vvvv and sometimes reboot windows before the patch will render again.
I’ve had this before and was one of the reasons I stopped using mesh distortion, just seeing all those screenshots reawakened my interest!