diff --git a/src/libraries/JANA/Engine/JSubeventArrow.h b/src/libraries/JANA/Engine/JSubeventArrow.h
index b643152ec..c54d6e589 100644
--- a/src/libraries/JANA/Engine/JSubeventArrow.h
+++ b/src/libraries/JANA/Engine/JSubeventArrow.h
@@ -218,12 +218,14 @@ void JMergeArrow<InputT, OutputT>::execute(JArrowMetrics& result, size_t locatio
 
     std::vector<std::shared_ptr<JEvent>*> outputs;
     for (const auto& input : inputs) {
+        LOG_TRACE(m_logger) << "JMergeArrow: Processing input with parent=" << input.parent << ", evt=" << (*(input.parent))->GetEventNumber() << ", sub=" << input.id << " and total=" << input.total << LOG_END;
         // Problem: Are we sure we are updating the event in a way which is effectively thread-safe?
         // Should we be doing this insert, or should the caller?
         (*(input.parent))->template Insert<OutputT>(input.data);
         if (input.total == 1) {
             // Goes straight into "ready"
             outputs.push_back(input.parent);
+            LOG_TRACE(m_logger) << "JMergeArrow: Finished parent=" << input.parent << ", evt=" << (*(input.parent))->GetEventNumber() << LOG_END;
         }
         else {
             auto pair = m_in_progress.find(input.parent);
@@ -237,6 +239,7 @@ void JMergeArrow<InputT, OutputT>::execute(JArrowMetrics& result, size_t locatio
                 else if (pair->second == 1) {
                     pair->second -= 1;
                     outputs.push_back(input.parent);
+                    LOG_TRACE(m_logger) << "JMergeArrow: Finished parent=" << input.parent << ", evt=" << (*(input.parent))->GetEventNumber() << LOG_END;
                 }
                 else {
                     pair->second -= 1;
@@ -244,18 +247,16 @@ void JMergeArrow<InputT, OutputT>::execute(JArrowMetrics& result, size_t locatio
             }
         }
     }
+    LOG_DEBUG(m_logger) << "MergeArrow consumed " << inputs.size() << " subevents, produced " << outputs.size() << " events" << LOG_END;
     auto end_latency_time = std::chrono::steady_clock::now();
-    auto out_status = OutQueue::Status::Ready;
 
-    size_t outputs_size = outputs.size();
-    if (outputs_size > 0) {
-        assert(m_outbox != nullptr);
-        out_status = m_outbox->push(outputs, downstream_accepts, location_id);
-    }
+    auto outputs_size = outputs.size();
+    auto out_status = m_outbox->push(outputs, downstream_accepts, location_id);
+
     auto end_queue_time = std::chrono::steady_clock::now();
 
     JArrowMetrics::Status status;
-    if (in_status == InQueue::Status::Ready && out_status == OutQueue::Status::Ready) {
+    if (in_status == InQueue::Status::Ready && out_status == OutQueue::Status::Ready && inputs.size() > 0) {
         status = JArrowMetrics::Status::KeepGoing;
     }
     else {