cut with surface - operation failed due to geometric condition

Hi,

I'm trying to build the attached model in which the combined surface should be used to cut part of the stack of individual sheets. I can't get the surface to behave - the Check tool is showing one open surface. I managed to close two others by knitting and re-knitting, but this one won't close.

Could anyone help in getting the cut with surface to work.

Br,

ST

SolidworksSurfacing