I am running my model, and I got the message "PCG has a matrix with 13127th diagonal element <=0". The model seems run and seems to converge but does not calcularte the piezometric heads. I defined the conductivity, head-constant BCs, recharge on inflow/outflow on top/bottom as 300 mm/year and the remaining material properties I used the default values.
I send a file with some more info.
How can I overcome this and get the model calculating the heads?