Convergence Issues with semi-permeable interface in dam 2d seepage analysis using PlaxFlow

Dear all,

I'm performing a 2D seepage analysis of a tailings dam using the 'PlaxFlow' module. Our design includes a geomembrane in the upstream face of the dam, we are currently modelling it as as an impervious interface element for. As a part of a sensibility analysis, I'm trying to model the geomembrane as low hydraulic conductivity interface (k = 1E-8 cm/s) but the model does not converge, It actually diverges, with flow error achieving several orders of magnitude before aborting by itself.

The interface properties that I'm using are:
Cross permeability: Semi permeable
Hydraulin resistance, d/k : 20E6
Drainage conductivity: dk [m3/s/m]: 0

The material adjacent to the interface have the following hydraulic conductivities:
Tailings (dam pond): 3E-5 cm/s
Core: 1E-5 cm/s

Thanks for your help.

Mauricio.