Same for me with a number of Cape species: we water them several times during their summer dormancy or they just shrivel off. Deeper pots means seedlings go deeper where they resist better excessive dessication. Out of a number of seedlings those that were deeper in the container were capable of sprouting for the second season. Of course once they are more than a year old everything is smooth. And yes, seed of this and several other species are more like black dust than "normal" seeds we are familiar with Use a very gritty mix.