diff --git a/src/SMESH/SMESH_MesherHelper.cxx b/src/SMESH/SMESH_MesherHelper.cxx
index 47feba98b..66edde438 100644
--- a/src/SMESH/SMESH_MesherHelper.cxx
+++ b/src/SMESH/SMESH_MesherHelper.cxx
@@ -860,6 +860,7 @@ bool SMESH_MesherHelper::CheckNodeU(const TopoDS_Edge&   E,
       {
         double r = Max( 0.5, 1 - tol*n->GetID()); // to get a unique u on edge
         u =  f*r + l*(1-r);
+        MESSAGE("curve.IsNull: " << u);
       }
     }
     else
@@ -895,6 +896,7 @@ bool SMESH_MesherHelper::CheckNodeU(const TopoDS_Edge&   E,
         }
         Quantity_Parameter U = projector->LowerDistanceParameter();
         u = double( U );
+        MESSAGE(" f " << f << " l " << l << " u " << u);
         curvPnt = curve->Value( u );
         dist = nodePnt.Distance( curvPnt );
         if ( distXYZ ) {
@@ -915,10 +917,12 @@ bool SMESH_MesherHelper::CheckNodeU(const TopoDS_Edge&   E,
       }
       else if ( fabs( u ) > numeric_limits<double>::min() )
       {
+        MESSAGE("fabs( u ) > numeric_limits<double>::min() ; u " << u << " f " << f << " l " << l);
         setPosOnShapeValidity( shapeID, true );
       }
       if (( u < f-tol || u > l+tol ) && force )
       {
+        MESSAGE("u < f-tol || u > l+tol  ; u " << u << " f " << f << " l " << l);
         // node is on vertex but is set on periodic but trimmed edge (issue 0020890)
         try
         {
diff --git a/src/StdMeshers/StdMeshers_Import_1D.cxx b/src/StdMeshers/StdMeshers_Import_1D.cxx
index 5de578356..59c11e550 100644
--- a/src/StdMeshers/StdMeshers_Import_1D.cxx
+++ b/src/StdMeshers/StdMeshers_Import_1D.cxx
@@ -620,7 +620,7 @@ namespace // INTERNAL STUFF
 bool StdMeshers_Import_1D::Compute(SMESH_Mesh & theMesh, const TopoDS_Shape & theShape)
 {
   if ( !_sourceHyp ) return false;
-
+  //MESSAGE("---------> StdMeshers_Import_1D::Compute");
   const vector<SMESH_Group*>& srcGroups = _sourceHyp->GetGroups();
   if ( srcGroups.empty() )
     return error("Invalid source groups");
@@ -650,9 +650,11 @@ bool StdMeshers_Import_1D::Compute(SMESH_Mesh & theMesh, const TopoDS_Shape & th
     {
       _gen->Compute(theMesh,v,/*anUpward=*/true);
       n = SMESH_Algo::VertexNode( v, tgtMesh );
+      //MESSAGE("_gen->Compute " << n);
       if ( !n ) return false; // very strange
     }
     vertexNodes.push_back( SMESH_TNodeXYZ( n ));
+    //MESSAGE("SMESH_Algo::VertexNode " << n->GetID() << " " << n->X() << " " << n->Y() << " " << n->Z() );
   }
 
   // import edges from groups
@@ -670,17 +672,19 @@ bool StdMeshers_Import_1D::Compute(SMESH_Mesh & theMesh, const TopoDS_Shape & th
     SMDS_ElemIteratorPtr srcElems = srcGroup->GetElements();
     vector<const SMDS_MeshNode*> newNodes;
     SMDS_MeshNode *tmpNode = helper.AddNode(0,0,0);
-    double u = 0;
+    double u = 0.314159; // "random" value between 0 and 1, avoid 0 and 1, false detection possible on edge restrictions
     while ( srcElems->more() ) // loop on group contents
     {
       const SMDS_MeshElement* edge = srcElems->next();
       // find or create nodes of a new edge
       newNodes.resize( edge->NbNodes() );
+      //MESSAGE("edge->NbNodes " << edge->NbNodes());
       newNodes.back() = 0;
       SMDS_MeshElement::iterator node = edge->begin_nodes();
       SMESH_TNodeXYZ a(edge->GetNode(0));
       // --- define a tolerance relative to the length of an edge
       double mytol = a.Distance(edge->GetNode(edge->NbNodes()-1))/25;
+      //mytol = max(1.E-5, 10*edgeTol); // too strict and not necessary
       //MESSAGE("mytol = " << mytol);
       for ( unsigned i = 0; i < newNodes.size(); ++i, ++node )
       {
@@ -697,22 +701,26 @@ bool StdMeshers_Import_1D::Compute(SMESH_Mesh & theMesh, const TopoDS_Shape & th
           for ( vNIt = vertexNodes.begin(); vNIt != vertexNodes.end(); ++vNIt)
             if ( vNIt->SquareDistance( *node ) < checktol)
             {
-              //MESSAGE("SquareDistance " << vNIt->SquareDistance( *node ) << " checktol " << checktol);
+              //MESSAGE("SquareDistance " << vNIt->SquareDistance( *node ) << " checktol " << checktol <<" "<<vNIt->X()<<" "<<vNIt->Y()<<" "<<vNIt->Z());
               (*n2nIt).second = vNIt->_node;
               vertexNodes.erase( vNIt );
               break;
             }
+            else if ( vNIt->SquareDistance( *node ) < 10*checktol)
+              MESSAGE("SquareDistance missed" << vNIt->SquareDistance( *node ) << " checktol " << checktol <<" "<<vNIt->X()<<" "<<vNIt->Y()<<" "<<vNIt->Z());
         }
         if ( !n2nIt->second )
         {
           // find out if node lies on theShape
+          //double dxyz[4];
           tmpNode->setXYZ( (*node)->X(), (*node)->Y(), (*node)->Z());
-          if ( helper.CheckNodeU( geomEdge, tmpNode, u, mytol, /*force=*/true ))
+          if ( helper.CheckNodeU( geomEdge, tmpNode, u, mytol, /*force=*/true)) // , dxyz )) // dxyz used for debug purposes
           {
             SMDS_MeshNode* newNode = tgtMesh->AddNode( (*node)->X(), (*node)->Y(), (*node)->Z());
             n2nIt->second = newNode;
             tgtMesh->SetNodeOnEdge( newNode, shapeID, u );
-            //MESSAGE("u=" << u);
+            //MESSAGE("u=" << u << " " << newNode->X()<< " " << newNode->Y()<< " " << newNode->Z());
+            //MESSAGE("d=" << dxyz[0] << " " << dxyz[1] << " " << dxyz[2] << " " << dxyz[3]);
           }
         }
         if ( !(newNodes[i] = n2nIt->second ))
@@ -730,7 +738,7 @@ bool StdMeshers_Import_1D::Compute(SMESH_Mesh & theMesh, const TopoDS_Shape & th
         newEdge = tgtMesh->AddEdge( newNodes[0], newNodes[1], newNodes[2] );
       else
         newEdge = tgtMesh->AddEdge( newNodes[0], newNodes[1]);
-      //MESSAGE("add Edge");
+      //MESSAGE("add Edge " << newNodes[0]->GetID() << " " << newNodes[1]->GetID());
       tgtMesh->SetMeshElementOnShape( newEdge, shapeID );
       e2e->insert( make_pair( edge, newEdge ));
     }