diff --git a/digitiser-aggregator/src/frame/cache.rs b/digitiser-aggregator/src/frame/cache.rs
index d169a4212..944d633e3 100644
--- a/digitiser-aggregator/src/frame/cache.rs
+++ b/digitiser-aggregator/src/frame/cache.rs
@@ -33,11 +33,11 @@ where
         digitiser_id: DigitizerId,
         metadata: &FrameMetadata,
         data: D,
-    ) {
+    ) -> Result<(), ()> {
         if let Some(latest_timestamp_dispatched) = self.latest_timestamp_dispatched {
             if metadata.timestamp <= latest_timestamp_dispatched {
                 warn!("Frame's timestamp earlier than or equal to the latest frame dispatched: {0} <= {1}", metadata.timestamp, latest_timestamp_dispatched);
-                return;
+                return Err(());
             }
         }
         let frame = {
@@ -85,6 +85,8 @@ where
         }) {
             warn!("Frame span linking failed {e}")
         }
+
+        Ok(())
     }
 
     pub(crate) fn poll(&mut self) -> Option<AggregatedFrame<D>> {
@@ -137,20 +139,28 @@ mod test {
         assert!(cache.poll().is_none());
 
         assert_eq!(cache.get_num_partial_frames(), 0);
-        cache.push(0, &frame_1, EventData::dummy_data(0, 5, &[0, 1, 2]));
+        assert!(cache
+            .push(0, &frame_1, EventData::dummy_data(0, 5, &[0, 1, 2]))
+            .is_ok());
         assert_eq!(cache.get_num_partial_frames(), 1);
 
         assert!(cache.poll().is_none());
 
-        cache.push(1, &frame_1, EventData::dummy_data(0, 5, &[3, 4, 5]));
+        assert!(cache
+            .push(1, &frame_1, EventData::dummy_data(0, 5, &[3, 4, 5]))
+            .is_ok());
 
         assert!(cache.poll().is_none());
 
-        cache.push(4, &frame_1, EventData::dummy_data(0, 5, &[6, 7, 8]));
+        assert!(cache
+            .push(4, &frame_1, EventData::dummy_data(0, 5, &[6, 7, 8]))
+            .is_ok());
 
         assert!(cache.poll().is_none());
 
-        cache.push(8, &frame_1, EventData::dummy_data(0, 5, &[9, 10, 11]));
+        assert!(cache
+            .push(8, &frame_1, EventData::dummy_data(0, 5, &[9, 10, 11]))
+            .is_ok());
 
         {
             let frame = cache.poll().unwrap();
@@ -198,15 +208,21 @@ mod test {
 
         assert!(cache.poll().is_none());
 
-        cache.push(0, &frame_1, EventData::dummy_data(0, 5, &[0, 1, 2]));
+        assert!(cache
+            .push(0, &frame_1, EventData::dummy_data(0, 5, &[0, 1, 2]))
+            .is_ok());
 
         assert!(cache.poll().is_none());
 
-        cache.push(1, &frame_1, EventData::dummy_data(0, 5, &[3, 4, 5]));
+        assert!(cache
+            .push(1, &frame_1, EventData::dummy_data(0, 5, &[3, 4, 5]))
+            .is_ok());
 
         assert!(cache.poll().is_none());
 
-        cache.push(8, &frame_1, EventData::dummy_data(0, 5, &[9, 10, 11]));
+        assert!(cache
+            .push(8, &frame_1, EventData::dummy_data(0, 5, &[9, 10, 11]))
+            .is_ok());
 
         assert!(cache.poll().is_none());
 
@@ -240,6 +256,38 @@ mod test {
         assert!(cache.poll().is_none());
     }
 
+    #[tokio::test]
+    async fn one_frame_in_one_frame_out_missing_digitiser_and_late_message_timeout() {
+        let mut cache = FrameCache::<EventData>::new(Duration::from_millis(100), vec![0, 1, 4, 8]);
+
+        let frame_1 = FrameMetadata {
+            timestamp: Utc::now(),
+            period_number: 1,
+            protons_per_pulse: 8,
+            running: true,
+            frame_number: 1728,
+            veto_flags: 4,
+        };
+        assert!(cache
+            .push(0, &frame_1, EventData::dummy_data(0, 5, &[0, 1, 2]))
+            .is_ok());
+        assert!(cache
+            .push(1, &frame_1, EventData::dummy_data(0, 5, &[3, 4, 5]))
+            .is_ok());
+        assert!(cache
+            .push(8, &frame_1, EventData::dummy_data(0, 5, &[9, 10, 11]))
+            .is_ok());
+
+        tokio::time::sleep(Duration::from_millis(105)).await;
+
+        let _ = cache.poll().unwrap();
+
+        //  This call to push should return an error
+        assert!(cache
+            .push(4, &frame_1, EventData::dummy_data(0, 5, &[6, 7, 8]))
+            .is_err());
+    }
+
     #[test]
     fn test_metadata_equality() {
         let mut cache = FrameCache::<EventData>::new(Duration::from_millis(100), vec![1, 2]);
@@ -268,11 +316,15 @@ mod test {
         assert_eq!(cache.frames.len(), 0);
         assert!(cache.poll().is_none());
 
-        cache.push(1, &frame_1, EventData::dummy_data(0, 5, &[0, 1, 2]));
+        assert!(cache
+            .push(1, &frame_1, EventData::dummy_data(0, 5, &[0, 1, 2]))
+            .is_ok());
         assert_eq!(cache.frames.len(), 1);
         assert!(cache.poll().is_none());
 
-        cache.push(2, &frame_2, EventData::dummy_data(0, 5, &[0, 1, 2]));
+        assert!(cache
+            .push(2, &frame_2, EventData::dummy_data(0, 5, &[0, 1, 2]))
+            .is_ok());
         assert_eq!(cache.frames.len(), 1);
         assert!(cache.poll().is_some());
     }
diff --git a/digitiser-aggregator/src/main.rs b/digitiser-aggregator/src/main.rs
index 0a8bf7eed..a0f984486 100644
--- a/digitiser-aggregator/src/main.rs
+++ b/digitiser-aggregator/src/main.rs
@@ -258,6 +258,7 @@ async fn process_kafka_message(
     metadata_protons_per_pulse = tracing::field::Empty,
     metadata_running = tracing::field::Empty,
     num_cached_frames = cache.get_num_partial_frames(),
+    is_discarded,
 ))]
 async fn process_digitiser_event_list_message(
     channel_send: &AggregatedFrameToBufferSender,
@@ -269,9 +270,12 @@ async fn process_digitiser_event_list_message(
             debug!("Event packet: metadata: {:?}", msg.metadata());
 
             // Push the current digitiser message to the frame cache, possibly creating a new partial frame
-            cache.push(msg.digitizer_id(), &metadata, msg.into());
+            let is_discarded = cache
+                .push(msg.digitizer_id(), &metadata, msg.into())
+                .is_err();
 
             record_metadata_fields_to_span!(&metadata, tracing::Span::current());
+            tracing::Span::current().record("is_discarded", is_discarded);
 
             cache_poll(channel_send, cache).await?;
         }