Unwanted water load appear in sectional face when the ground surface formed by importing

Hi, I am a newbie in Plaxis 3D. I am setting the model of deep excavation with lateral support.  

First, I creat the soil/existing ground by borehole only, and i set some volume to deactivate since the ground surface is not flat. And I creat all excavation volume by "structure: surface with extrude tool", it is not accurate due to the excavated surface with the different gradient in real case. The result generated is reasonably close.

Then, I found that the existing ground surface can be imported in borehole setting. I imported the surface in DXF format and it looks really great!! After that (re-calculation), it fails just in stage 1 (inserting sheet pile wall without any excavation). I dont know whats going on and i found that there are some external water load adding to the sectional face, which does not appear in my first method.

Please help.... Thank you.

Best Regards,