Index: trunk/src/org/openstreetmap/josm/data/validation/OsmValidator.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/validation/OsmValidator.java	(revision 16246)
+++ trunk/src/org/openstreetmap/josm/data/validation/OsmValidator.java	(revision 16247)
@@ -235,4 +235,6 @@
                 Logging.log(Logging.LEVEL_ERROR, "Unable to load ignored errors", e);
             }
+            // see #19053: remove invalid entry
+            ignoredErrors.remove("3000");
         }
     }
Index: trunk/src/org/openstreetmap/josm/gui/dialogs/ValidatorDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/dialogs/ValidatorDialog.java	(revision 16246)
+++ trunk/src/org/openstreetmap/josm/gui/dialogs/ValidatorDialog.java	(revision 16247)
@@ -411,5 +411,7 @@
         lastSelectedNode = node;
         if (node != null) {
+            final Set<String> codes = new HashSet<>();
             ValidatorTreePanel.visitTestErrors(node, error -> {
+                codes.add(error.getIgnoreSubGroup()); // see #19053
                 error.setSelected(true);
 
@@ -423,5 +425,5 @@
             selectAction.setEnabled(true);
             if (ignoreAction != null) {
-                ignoreAction.setEnabled(!(node.getUserObject() instanceof Severity));
+                ignoreAction.setEnabled(!(node.getUserObject() instanceof Severity) && codes.size() <= 1);
             }
         }