is something off with the geometry? trying to rotate the square a bit...

NonLinearEVP/NonLinearEVP.geo

@@ -114,6 +114,7 @@ If (flag_Tmesh==0)
     Plane Surface(3) = {2, 3};
     Line Loop(4) = {9, 10, 11, 3};
     Plane Surface(4) = {-4};
+    Rotate {{0, 0, 1}, {0, 0, 0}, 2.*Pi/180.} { Surface{ 2 } ; }
     Periodic Line { 14,18,19,20,11 } = {12,15,16,17,9 } Translate {a_lat,0,0} ;
     Physical Line("SCATBOUND",1005)    = {21,22,23,24,25,26,27,28}; // bound for lag
   EndIf