Why do these irregularities appear in the trench?

Hello all. I’m checking the trench smoothing in a nested grid. I don’t know way I obtain, consistently at different latitudes and only in the nested grid, some irregularities in the trench as seen in the figure attached (croco_grd line). Do you know why this happens?, and how could I fix this problem? Thanks in advance.

Hi Eric,

Have you tried different values for