Debug endpoint mismatches

diff --git a/src/ripple/peerfinder/impl/Logic.h b/src/ripple/peerfinder/impl/Logic.h
index 812e5d2..88dd5c9 100644
--- a/src/ripple/peerfinder/impl/Logic.h
+++ b/src/ripple/peerfinder/impl/Logic.h
@@ -280,6 +280,22 @@ public:
             if (iter != state->slots.end ())
             {
                 Slot::ptr const& self (iter->second);
+                if ((self->local_endpoint () != boost::none) &&
+                    (self->local_endpoint () != remote_endpoint))
+                {
+                    // This is most odd. We have received an incoming connection,
+                    // and we have its local endpoint in our slot table.
+                    // So we expect that we have two ends of the same connection.
+                    // Yet our remote endpoint does not match the other connection's
+                    // local endpoint.
+                    m_journal.fatal << "Local endpoint mismatch:";
+                    m_journal.fatal <<
+                        "1) local:" << local_endpoint <<
+                        " remote:" << remote_endpoint;
+                    m_journal.fatal <<
+                        "2) local:" << self->local_endpoint () <<
+                        " remote:" << self->remote_endpoint ();
+                }
                 assert ((self->local_endpoint () == boost::none) ||
                     (self->local_endpoint () == remote_endpoint));
                 if (m_journal.warning) m_journal.warning << beast::leftw (18) <<