diff --git a/android/app/src/test/java/com/openipc/decoder/JieliTest.java b/android/app/src/test/java/com/openipc/decoder/JieliTest.java
index 0576f43..e3d460a 100644
--- a/android/app/src/test/java/com/openipc/decoder/JieliTest.java
+++ b/android/app/src/test/java/com/openipc/decoder/JieliTest.java
@@ -799,7 +799,9 @@ public void noVideoListensElsewhereAndAsksAgain() throws Exception {
         Jieli.noVideoMs = 300;
         Jieli.reopenMs = 700;
         Jieli.diagnosticPorts = new int[] {diag};
-        Jieli.diagnosticMs = 500;
+        // The port lives this long (then up to a receive timeout more): long enough for the
+        // packet below to arrive on a loaded CI runner, where a pause of a second failed it (#257)
+        Jieli.diagnosticMs = 3000;
         try (FakeToy toy = new FakeToy(60000, true)) {
             toy.rtpPort = rtp;
             toy.sendVideo = false;
@@ -813,13 +815,16 @@ public void noVideoListensElsewhereAndAsksAgain() throws Exception {
                 byte[] p = {(byte) 0x80, 97, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 9};
                 u.send(new DatagramPacket(p, p.length, new InetSocketAddress(LOOPBACK, diag)));
             }
-            until = now() + 3000;
+            // Generous on a loaded runner; the asserts read the snapshot the loop stopped on
+            // (Qodo on #259)
+            until = now() + 8000;
+            Map<String, Object> st = r.client.stats();
             while (now() < until && (Collections.frequency(toy.topics(), Jieli.OPEN_RT_STREAM) < 2
-                    || r.client.stats().get("diagnostic_ports") == null)) {
+                    || st.get("diagnostic_ports") == null)) {
                 Thread.sleep(20);
+                st = r.client.stats();
             }
             assertTrue(Collections.frequency(toy.topics(), Jieli.OPEN_RT_STREAM) >= 2);
-            Map<String, Object> st = r.client.stats();
             @SuppressWarnings("unchecked")
             Map<String, Object> d = (Map<String, Object>) st.get("diagnostic_ports");
             assertNotNull(d);
@@ -827,7 +832,7 @@ public void noVideoListensElsewhereAndAsksAgain() throws Exception {
             Map<String, Object> one = (Map<String, Object>) d.get(String.valueOf(diag));
             assertEquals(1, one.get("packets"));
             // The diagnostic port is freed after diagnosticMs while the session goes on
-            until = now() + 3000;
+            until = now() + 6000;
             boolean freed = false;
             while (now() < until && !freed) {
                 try (DatagramSocket again = new DatagramSocket(diag, LOOPBACK)) {
diff --git a/android/app/src/test/java/com/openipc/decoder/RtpListenerTest.java b/android/app/src/test/java/com/openipc/decoder/RtpListenerTest.java
index bcf8cfb..34636b9 100644
--- a/android/app/src/test/java/com/openipc/decoder/RtpListenerTest.java
+++ b/android/app/src/test/java/com/openipc/decoder/RtpListenerTest.java
@@ -28,6 +28,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
@@ -101,9 +102,11 @@ public void badUrlsAreRefused() {
     // ====================== Session ======================
 
     private static final class Recorder implements RtspSession.Callback {
-        final List<String> statuses = Collections.synchronizedList(new ArrayList<>());
-        final List<Sdp> sdps = Collections.synchronizedList(new ArrayList<>());
-        final List<Integer> pts = Collections.synchronizedList(new ArrayList<>());
+        // Filled by the session thread while the test reads them: Collections.frequency() and
+        // for-each iterate, which a synchronizedList does not guard (#257)
+        final List<String> statuses = new CopyOnWriteArrayList<>();
+        final List<Sdp> sdps = new CopyOnWriteArrayList<>();
+        final List<Integer> pts = new CopyOnWriteArrayList<>();
         volatile CountDownLatch latch = new CountDownLatch(3);
 
         @Override public void onStatus(String status) { statuses.add(status); }