Index: /applications/editors/josm/plugins/terracer/src/org/openstreetmap/josm/plugins/terracer/TerracerAction.java
===================================================================
--- /applications/editors/josm/plugins/terracer/src/org/openstreetmap/josm/plugins/terracer/TerracerAction.java	(revision 35557)
+++ /applications/editors/josm/plugins/terracer/src/org/openstreetmap/josm/plugins/terracer/TerracerAction.java	(revision 35558)
@@ -440,4 +440,6 @@
         // remove housenumbers as they have been deleted
         newAssociatedStreet.removeMembersFor(housenumbers);
+        // see #19853 avoid to duplicate existing members
+        newAssociatedStreet.removeMembersFor(ways);
         for (Way w : ways) {
             newAssociatedStreet.addMember(new RelationMember("house", w));