Index: /trunk/src/org/openstreetmap/josm/gui/tagging/presets/TaggingPresetValidation.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/tagging/presets/TaggingPresetValidation.java	(revision 19159)
+++ /trunk/src/org/openstreetmap/josm/gui/tagging/presets/TaggingPresetValidation.java	(revision 19160)
@@ -45,6 +45,10 @@
      */
     static void validateAsync(OsmPrimitive original, JLabel validationLabel, List<Tag> changedTags) {
-        OsmPrimitive primitive = applyChangedTags(original, changedTags);
-        MainApplication.worker.execute(() -> validate(primitive, validationLabel));
+        MainApplication.worker.execute(() -> {
+            // applyChangedTags can be very expensive if a relation gets involved, so it must be done in
+            // a separate thread. This is becuase it clones all potentially affected objects.
+            OsmPrimitive primitive = applyChangedTags(original, changedTags);
+            validate(primitive, validationLabel);
+        });
     }
 
Index: /trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/MultiSelect.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/MultiSelect.java	(revision 19159)
+++ /trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/MultiSelect.java	(revision 19160)
@@ -95,5 +95,9 @@
         p.add(sp, GBC.eol().fill(GBC.HORIZONTAL)); // NOSONAR
 
-        list.addListSelectionListener(l -> support.fireItemValueModified(this, key, getSelectedItem().value));
+        list.addListSelectionListener(l -> {
+            if (!l.getValueIsAdjusting()) {
+                support.fireItemValueModified(this, key, getSelectedItem().value);
+            }
+        });
         list.setToolTipText(getKeyTooltipText());
         list.applyComponentOrientation(OrientationAction.getValueOrientation(key));
Index: /trunk/src/org/openstreetmap/josm/io/CertificateAmendment.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/io/CertificateAmendment.java	(revision 19159)
+++ /trunk/src/org/openstreetmap/josm/io/CertificateAmendment.java	(revision 19160)
@@ -22,5 +22,4 @@
 import java.security.cert.TrustAnchor;
 import java.security.cert.X509Certificate;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;