Really great aha moment for this one! The way to approach this correctly is the last thing that I would have considered.
I was stuck in a brilliant 2 off the day before, this made me appreciate again the vast amount of serious effort that was put into the level series. 7th DEM done.
This is the first from the series Deux Ex Machina that I managed to solve. Very difficult to see, indeed. Great level! (22 tries, but many MANY tries on some others from this series, before :))