Scaling issues related to the smoothing length iterations
Discussion triggered by @nnrw56's question.
The maximal change in volume a particle can have over the course of a time-step is set by the parameter
SPH:
max_volume_change: 2.
The default value is 2 if nothing is specified. That leads to a maximal change in h of 1.26 over the course of a time-step.
Setting this to a smaller value leads to particles being active more often but might make some of the time-steps cheaper.