Thanks for following up.

I suspect my initialization being incorrect, I use hybrid, and would like to have your openion on that too please.

But apart from that, I am using no DEM, because, despite keeping DDPM on, I am using low particle VF, just to keep on the safe side. (Or is it low VF of DDPM that leads the model to divergence?). And I am already using separate timestep for particles. :*(