diff --git a/src/org/jgroups/protocols/UNICAST3.java b/src/org/jgroups/protocols/UNICAST3.java
index ee561a4818..87a0cd1055 100644
--- a/src/org/jgroups/protocols/UNICAST3.java
+++ b/src/org/jgroups/protocols/UNICAST3.java
@@ -6,7 +6,9 @@
 import org.jgroups.annotations.ManagedOperation;
 import org.jgroups.annotations.Property;
 import org.jgroups.conf.AttributeType;
+import org.jgroups.protocols.relay.RELAY;
 import org.jgroups.stack.Protocol;
+import org.jgroups.stack.ProtocolStack;
 import org.jgroups.util.*;
 
 import java.util.*;
@@ -124,15 +126,19 @@ public class UNICAST3 extends Protocol implements AgeOutCache.Handler<Address> {
     @ManagedAttribute(description="tracing is enabled or disabled for the given log",writable=true)
     protected boolean is_trace=log.isTraceEnabled();
 
+    @ManagedAttribute(description="Whether or not a RELAY protocol was found below in the stack")
+    protected boolean relay_present;
+
     /* --------------------------------------------- Fields ------------------------------------------------ */
 
 
-    protected final ConcurrentMap<Address, SenderEntry>   send_table=Util.createConcurrentMap();
-    protected final ConcurrentMap<Address, ReceiverEntry> recv_table=Util.createConcurrentMap();
+    protected final ConcurrentMap<Address,SenderEntry>   send_table=Util.createConcurrentMap();
+    protected final ConcurrentMap<Address,ReceiverEntry> recv_table=Util.createConcurrentMap();
 
     protected final ReentrantLock          recv_table_lock=new ReentrantLock();
 
-    /** Used by the retransmit task to keep the last retransmitted seqno per sender (https://issues.redhat.com/browse/JGRP-1539) */
+    /** Used by the retransmit task to keep the last retransmitted seqno per member (applicable only
+     * for received messages (ReceiverEntry)): https://issues.redhat.com/browse/JGRP-1539 */
     protected final Map<Address,Long>      xmit_task_map=new HashMap<>();
 
     /** RetransmitTask running every xmit_interval ms */
@@ -171,6 +177,12 @@ public class UNICAST3 extends Protocol implements AgeOutCache.Handler<Address> {
 
     protected static final BiConsumer<MessageBatch,Message> BATCH_ACCUMULATOR=MessageBatch::add;
 
+    /** Used for testing only! */
+    public Table<Message> getSendWindow(Address target) {
+        SenderEntry entry=send_table.get(target);
+        return entry != null? entry.msgs : null;
+    }
+
     @ManagedAttribute(description="Returns the number of outgoing (send) connections")
     public int getNumSendConnections() {
         return send_table.size();
@@ -409,6 +421,7 @@ public void init() throws Exception {
                 throw new IllegalStateException(e);
             }
         }
+        relay_present=ProtocolStack.findProtocol(this.down_prot, RELAY.class) != null;
     }
 
 
@@ -617,7 +630,8 @@ public Object down(Event evt) {
 
                 if(!non_members.isEmpty()) {
                     log.trace("%s: closing connections of non members %s", local_addr, non_members);
-                    non_members.forEach(this::closeConnection);
+                    // remove all non members, except those from remote sites: https://issues.redhat.com/browse/JGRP-2729
+                    non_members.stream().filter(this::isLocal).forEach(this::closeConnection);
                 }
                 if(!new_members.isEmpty()) {
                     for(Address mbr: new_members) {
@@ -706,8 +720,18 @@ public Object down(Message msg) {
     protected boolean isLocalSiteMaster(Address dest) {
         // quick check to avoid the use of 'instanceof'; will be removed once https://bugs.openjdk.org/browse/JDK-8180450
         // has been fixed (in Java 22, should be backported to older versions)
-        if(dest.isSiteMaster()) {
-            Object ret=down_prot.down(new Event(Event.IS_LOCAL, dest));
+        if(relay_present && dest.isSiteMaster()) {
+            Object ret=down_prot.down(new Event(Event.IS_LOCAL_SITEMASTER, dest));
+            return ret != null && (Boolean)ret;
+        }
+        return false;
+    }
+
+    protected boolean isLocal(Address addr) {
+        // quick check to avoid the use of 'instanceof'; will be removed once https://bugs.openjdk.org/browse/JDK-8180450
+        // has been fixed (in Java 22, should be backported to older versions)
+        if(relay_present && addr.isSiteAddress()) {
+            Object ret=down_prot.down(new Event(Event.IS_LOCAL, addr));
             return ret != null && (Boolean)ret;
         }
         return false;