diff --git a/src/db/db/dbHierNetworkProcessor.cc b/src/db/db/dbHierNetworkProcessor.cc
index 1bb053cbc..621a4aea3 100644
--- a/src/db/db/dbHierNetworkProcessor.cc
+++ b/src/db/db/dbHierNetworkProcessor.cc
@@ -1347,30 +1347,37 @@ private:
       return;
     }
 
-    db::ICplxTrans i1t = i1.complex_trans ();
-    db::ICplxTrans tt1 = t1 * i1t;
+    InstanceToInstanceInteraction ii_key;
+    db::ICplxTrans i1t, i2t;
 
-    db::ICplxTrans i2t = i2.complex_trans ();
-    db::ICplxTrans tt2 = t2 * i2t;
+    {
+      i1t = i1element.at_end () ? i1.complex_trans () : i1.complex_trans (*i1element);
+      db::ICplxTrans tt1 = t1 * i1t;
 
-    db::ICplxTrans tt21 = tt1.inverted () * tt2;
-    InstanceToInstanceInteraction ii_key (i1.cell_index (), i1.cell_inst ().delegate (), i2.cell_index (), i2.cell_inst ().delegate (), tt21);
+      i2t = i2element.at_end () ? i2.complex_trans () : i2.complex_trans (*i2element);
+      db::ICplxTrans tt2 = t2 * i2t;
 
-    instance_interaction_cache_type::iterator ii = mp_instance_interaction_cache->find (ii_key);
-    if (ii != mp_instance_interaction_cache->end ()) {
+      db::ICplxTrans tt21 = tt1.inverted () * tt2;
+      ii_key = InstanceToInstanceInteraction (i1.cell_index (), (! i1element.at_end () || i1.size () == 1) ? 0 : i1.cell_inst ().delegate (),
+                                              i2.cell_index (), (! i2element.at_end () || i2.size () == 1) ? 0 : i2.cell_inst ().delegate (),
+                                              tt21);
+
+      instance_interaction_cache_type::iterator ii = mp_instance_interaction_cache->find (ii_key);
+      if (ii != mp_instance_interaction_cache->end ()) {
+
+        //  use cached interactions
+        interacting_clusters = ii->second;
+        for (std::list<std::pair<ClusterInstance, ClusterInstance> >::iterator i = interacting_clusters.begin (); i != interacting_clusters.end (); ++i) {
+          //  translate the property IDs
+          i->first.set_inst_prop_id (i1.prop_id ());
+          i->first.transform (i1t);
+          i->second.set_inst_prop_id (i2.prop_id ());
+          i->second.transform (i2t);
+        }
+
+        return;
 
-      //  use cached interactions
-      interacting_clusters = ii->second;
-      for (std::list<std::pair<ClusterInstance, ClusterInstance> >::iterator i = interacting_clusters.begin (); i != interacting_clusters.end (); ++i) {
-        //  translate the property IDs
-        i->first.set_inst_prop_id (i1.prop_id ());
-        i->first.transform (i1t);
-        i->second.set_inst_prop_id (i2.prop_id ());
-        i->second.transform (i2t);
       }
-
-      return;
-
     }
 
     //  array interactions
diff --git a/src/db/db/dbHierNetworkProcessor.h b/src/db/db/dbHierNetworkProcessor.h
index 057e2e649..49e9405fb 100644
--- a/src/db/db/dbHierNetworkProcessor.h
+++ b/src/db/db/dbHierNetworkProcessor.h
@@ -765,6 +765,10 @@ struct InstanceToInstanceInteraction
     : ci1 (_ci1), ci2 (_ci2), array1 (_array1), array2 (_array2), t21 (_t21)
   { }
 
+  InstanceToInstanceInteraction ()
+    : ci1 (0), ci2 (0), array1 (0), array2 (0)
+  { }
+
   bool operator== (const InstanceToInstanceInteraction &other) const
   {
     return ci1 == other.ci1 && ci2 == other.ci2 && t21.equal (other.t21) &&
diff --git a/src/db/db/gsiDeclDbLayoutToNetlist.cc b/src/db/db/gsiDeclDbLayoutToNetlist.cc
index eab15bca5..dc65068cc 100644
--- a/src/db/db/gsiDeclDbLayoutToNetlist.cc
+++ b/src/db/db/gsiDeclDbLayoutToNetlist.cc
@@ -329,7 +329,7 @@ Class<db::LayoutToNetlist> decl_dbLayoutToNetlist ("db", "LayoutToNetlist",
   gsi::method ("global_net_name", &db::LayoutToNetlist::global_net_name, gsi::arg ("global_net_id"),
     "@brief Gets the global net name for the given global net ID."
   ) +
-  gsi::method ("extract_netlist", &db::LayoutToNetlist::extract_netlist, gsi::arg ("join_net_names", std::string ()), gsi::arg ("include_floating_subcircuits", false),
+  gsi::method ("extract_netlist", &db::LayoutToNetlist::extract_netlist, gsi::arg ("join_net_names", std::string (), "\"\""), gsi::arg ("include_floating_subcircuits", false),
     "@brief Runs the netlist extraction\n"
     "'join_net_names' is a glob expression for labels. Nets on top level carrying the same label which matches this glob "
     "expression will be connected implicitly even if there is no physical connection. This feature is useful to simulate a connection "
@@ -359,12 +359,14 @@ Class<db::LayoutToNetlist> decl_dbLayoutToNetlist ("db", "LayoutToNetlist",
     "@brief Runs the netlist extraction\n"
     "This method runs the netlist extraction like the two-parameter version. In addition to the latter, this method "
     "can be given a per-cell net label joining specification in 'join_net_names_per_cell'. The keys of this array "
-    "are cell names or cell names or cell name match expressions (glob style). The values are lable match expressions.\n"
+    "are cell names or cell names or cell name match expressions (glob style). The values are label match expressions.\n"
     "\n"
     "If not an empty string, the 'join_net_names' label match expression is applied to the top cell. For all non-top cells "
     "the per-cell label match expression is applied and determines what labels are joined into single nets. "
     "As the keys of 'join_net_names_per_cell' are glob expressions, a single cell may fall into more than one category. In this "
-    "case, the label match pattern are combined. In any case, the 'join_net_names' has priority for the top cell."
+    "case, the label match pattern are combined. In any case, the 'join_net_names' has priority for the top cell.\n"
+    "\n"
+    "This variant of 'extract_netlist' has been introduced in version 0.26.2."
   ) +
   gsi::method_ext ("internal_layout", &l2n_internal_layout,
     "@brief Gets the internal layout\n"
diff --git a/src/db/unit_tests/dbHierNetworkProcessorTests.cc b/src/db/unit_tests/dbHierNetworkProcessorTests.cc
index 07ca63197..6f9743225 100644
--- a/src/db/unit_tests/dbHierNetworkProcessorTests.cc
+++ b/src/db/unit_tests/dbHierNetworkProcessorTests.cc
@@ -1275,3 +1275,9 @@ TEST(118_HierClustersMeanderArrays)
   run_hc_test (_this, "meander.gds.gz", "meander_au1.gds");
   run_hc_test_with_backannotation (_this, "meander.gds.gz", "meander_au2.gds");
 }
+
+TEST(119_HierClustersCombArrays)
+{
+  run_hc_test (_this, "comb.gds", "comb_au1.gds");
+  run_hc_test_with_backannotation (_this, "comb.gds", "comb_au2.gds");
+}
diff --git a/src/lay/lay/layGSIHelpProvider.cc b/src/lay/lay/layGSIHelpProvider.cc
index ee14780c4..48121cd71 100644
--- a/src/lay/lay/layGSIHelpProvider.cc
+++ b/src/lay/lay/layGSIHelpProvider.cc
@@ -796,7 +796,6 @@ method_arguments (const gsi::MethodBase *method, const gsi::ClassBase *cls_obj,
         if (i > 0) {
           r += ",";
           r += sep;
-          r += "&nbsp;";
         }
         r += escape_xml (doc.args [i]);
       }
@@ -816,7 +815,6 @@ method_arguments (const gsi::MethodBase *method, const gsi::ClassBase *cls_obj,
       if (n > 0) {
         r += ",";
         r += sep;
-        r += "&nbsp;";
       }
       r += type_to_s (*a, linked, false);
       r += " ";
@@ -1312,7 +1310,7 @@ GSIHelpProvider::produce_class_doc (const std::string &cls) const
     if (! attr.empty ()) {
       os << "<i>[" << escape_xml (attr) << "] </i>";
     }
-    os << method_return (i->second.first, method_doc, true) << " <b> " << escape_xml (i->first) << " </b> " << method_arguments (i->second.first, cls_obj, method_doc, true, "");
+    os << method_return (i->second.first, method_doc, true) << " <b> " << escape_xml (i->first) << " </b> " << method_arguments (i->second.first, cls_obj, method_doc, true, " ");
     os << "</p>" << std::endl;
 
     os << "<p><b>" << tl::to_string (QObject::tr ("Description")) << "</b>: " << replace_references (escape_xml (method_doc.brief_doc), cls_obj) << "</p>" << std::endl;