VrayMultiSub and Material ID (random)

[rival]

I'm not getting randomisation when I use a VrayMultiSub (Face material ID) with a Material ID (random). All particle shapes have a single color in the render. However, when I use a MultiSubMat, then it behaves as expected; eg, random colors according to the IDs assigned in the flow.

In fact, I just can't seem to get the VrayMultiSub to play nice with Tyflow at all. Even using its own random modes, particle shapes are always a single color. What's going on here?

Tyflow version is 0,16134
Vray 5