diff --git a/src/ifcgeom/function_item_evaluator.cpp b/src/ifcgeom/function_item_evaluator.cpp
index f924dae4a6..9bacf94ac0 100644
--- a/src/ifcgeom/function_item_evaluator.cpp
+++ b/src/ifcgeom/function_item_evaluator.cpp
@@ -122,7 +122,7 @@ struct gradient_fn_evaluator : public fn_evaluator {
         // Put curvature back into the solution matrix
         // curvature for vertical is in column 0, need it to be in column 1
         // so it doesn't add to curvature for horizontal
-        std::swap(vertical_curvature(3, 0), vertical_curvature(3, 1));
+        std::swap(vertical_curvature(0), vertical_curvature(1));
         m.row(3) = horizontal_curvature + vertical_curvature;
 
         return m;
diff --git a/src/ifcgeom/mapping/IfcOffsetCurveByDistance.cpp b/src/ifcgeom/mapping/IfcOffsetCurveByDistance.cpp
index e42cc840a6..a506049a95 100644
--- a/src/ifcgeom/mapping/IfcOffsetCurveByDistance.cpp
+++ b/src/ifcgeom/mapping/IfcOffsetCurveByDistance.cpp
@@ -39,15 +39,29 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcOffsetCurveByDistances* inst
     auto first_offset_value = *(offset_values->begin());
 
     auto basis_curve = inst->BasisCurve();
-    auto curve = taxonomy::dcast<taxonomy::function_item>(map(basis_curve));
-    if (!curve) {
+
+//    // IfcOffsetCurveByDistances can be based on another IfcOffsetCurveByDistances, an IfcGradientCurve, or an IfcCompositeCurve
+//    // When based on IfcOffsetCurveByDistances, it creates a chain of curves that we must navigate down to the base curve.
+//    // The source curve is IfcGradientCurve or IfcCompositeCurve. This loop drills down to the base curve.
+//    while (auto offset_curve = basis_curve->as<IfcSchema::IfcOffsetCurveByDistances>()) {
+//        basis_curve = offset_curve;
+//    }
+//
+//#if defined SCHEMA_HAS_IfcGradientCurve
+//    if (auto gc = basis_curve->as<IfcSchema::IfcGradientCurve>()) {
+//        basis_curve = gc->BaseCurve();
+//    }
+//#endif
+
+    auto basis_curve_fn = taxonomy::dcast<taxonomy::function_item>(map(basis_curve));
+    if (!basis_curve_fn) {
         // Only implement on alignment curves
         Logger::Warning("IfcOffsetCurveByDistances is only implemented for BasisCurves curves based on taxonomy::function_item", inst);
         return nullptr;
     }
 
-    double start = curve->start();
-    double basis_curve_length = curve->length();
+    double start = basis_curve_fn->start();
+    double basis_curve_length = basis_curve_fn->length();
 
     taxonomy::piecewise_function::spans_t offset_spans;
 
@@ -56,6 +70,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcOffsetCurveByDistances* inst
 #else
    double first_distance = *first_offset_value->DistanceAlong()->as<IfcSchema::IfcLengthMeasure>();
 #endif
+   first_distance *= length_unit_;
 
    if (first_distance < 0.0) {
         Logger::Warning("IfcOffsetCurveByDistance first offset value is before the start of the curve.");
@@ -83,31 +98,28 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcOffsetCurveByDistances* inst
     auto prev = std::prev(next);
     auto end = offset_values->end();
     for (; next != end; prev++, next++) {
-#if defined SCHEMA_HAS_IfcPointByDistanceExpression
-        if ((*prev)->BasisCurve() != basis_curve || (*next)->BasisCurve() != basis_curve) {
-            Logger::Error("All offsets from a IfcOffsetCurveByDistances must refer to the same BasisCurve");
-        }
-#endif
-
 #if defined SCHEMA_HAS_IfcDistanceExpression
-        double dn = (*next)->DistanceAlong();
         double dp = (*prev)->DistanceAlong();
+        double dn = (*next)->DistanceAlong();
 #else
-        double dn = *(*next)->DistanceAlong()->as<IfcSchema::IfcLengthMeasure>();
         double dp = *(*prev)->DistanceAlong()->as<IfcSchema::IfcLengthMeasure>();
+        double dn = *(*next)->DistanceAlong()->as<IfcSchema::IfcLengthMeasure>();
 #endif
-        if ((dp < 0.0 || basis_curve_length < dp) 
+        dp *= length_unit_;
+        dn *= length_unit_;
+
+        if ((dp < 0.0 || basis_curve_length < dp)  // previous is out of range
              || 
-            (dn < 0.0 || basis_curve_length < dn)
+            (dn < 0.0 || basis_curve_length < dn) // next is out of range
            ||
-            (dn < dp)
+            (dn < dp) // next is before previous
            )
         {
             Logger::Warning("IfcOffsetCurveByDistance offset value is out of bounds.");
             continue;
         }
 
-        double l = (dn - dp)*length_unit_;
+        double l = (dn - dp);
         double yn = (*next)->OffsetLateral().get_value_or(0.0) * length_unit_;
         double yp = (*prev)->OffsetLateral().get_value_or(0.0) * length_unit_;
         double zn = (*next)->OffsetVertical().get_value_or(0.0) * length_unit_;
@@ -152,7 +164,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcOffsetCurveByDistances* inst
 
    auto offsets = taxonomy::make<taxonomy::piecewise_function>(start,offset_spans);
 
-   auto fn = taxonomy::make<taxonomy::offset_function>(curve, offsets);
+   auto fn = taxonomy::make<taxonomy::offset_function>(basis_curve_fn, offsets);
    return fn;
 }
 
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_offset_curve.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_offset_curve.py
index 1667a7b352..c41fe12c28 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_offset_curve.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_offset_curve.py
@@ -54,9 +54,9 @@ def create_as_offset_curve(
     _create_offset_curve_representation(file, alignment, offsets)
 
     # define stationing
-    name = ifcopenshell.util.alignment.station_as_string(file, start_station)
-    referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, start_station, name)
-    ifcopenshell.api.nest.reorder_nesting(file, referent, -1, 0)
+    #name = ifcopenshell.util.alignment.station_as_string(file, start_station)
+    #referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, start_station, name)
+    #ifcopenshell.api.nest.reorder_nesting(file, referent, -1, 0)
 
     # IFC 4.1.4.1.1 Alignment Aggregation To Project
     project = file.by_type("IfcProject")[0]