diff --git a/src/dds/rs-dds-sensor-proxy.cpp b/src/dds/rs-dds-sensor-proxy.cpp
index 06f3ce4a37..e637f2a62e 100644
--- a/src/dds/rs-dds-sensor-proxy.cpp
+++ b/src/dds/rs-dds-sensor-proxy.cpp
@@ -473,6 +473,9 @@ void dds_sensor_proxy::add_frame_metadata( frame * const f,
 
 void dds_sensor_proxy::start( rs2_frame_callback_sptr callback )
 {
+    // Remove leftovers from previous starts.
+    _streaming_by_name.clear();
+
     for( auto & profile : sensor_base::get_active_streams() )
     {
         auto streamit = _streams.find( sid_index( profile->get_unique_id(), profile->get_stream_index() ) );
@@ -498,6 +501,7 @@ void dds_sensor_proxy::start( rs2_frame_callback_sptr callback )
                     invoke_new_frame( static_cast< frame * >( fh.release() ), nullptr, nullptr );
                 }
             } );
+        streaming.syncer.start();
 
         if( auto dds_video_stream = std::dynamic_pointer_cast< realdds::dds_video_stream >( dds_stream ) )
         {
@@ -547,7 +551,10 @@ void dds_sensor_proxy::stop()
         dds_stream->stop_streaming();
         dds_stream->close();
 
-        _streaming_by_name[dds_stream->name()].syncer.on_frame_ready( nullptr );
+        // Nullifing the lambda is commented out because we don't want to nullify in middle of user callback (that might
+        // be long) instead we use start/stop.
+        //_streaming_by_name[dds_stream->name()].syncer.on_frame_ready( nullptr );
+        _streaming_by_name[dds_stream->name()].syncer.stop();
 
         if( auto dds_video_stream = std::dynamic_pointer_cast< realdds::dds_video_stream >( dds_stream ) )
         {
@@ -566,7 +573,8 @@ void dds_sensor_proxy::stop()
 
     // Must be done after dds_stream->stop_streaming or we will need to add validity checks to on_data_available,
     // and after software_sensor::stop cause to make sure _is_streaming is false
-    _streaming_by_name.clear();
+    // Removed here, same reason of killing on_frame_ready lambda instance. Moved to start()
+    //_streaming_by_name.clear();
 }
 
 
diff --git a/third-party/realdds/include/realdds/dds-metadata-syncer.h b/third-party/realdds/include/realdds/dds-metadata-syncer.h
index 40734e0c9a..bce6a88178 100644
--- a/third-party/realdds/include/realdds/dds-metadata-syncer.h
+++ b/third-party/realdds/include/realdds/dds-metadata-syncer.h
@@ -8,6 +8,7 @@
 #include <memory>
 #include <mutex>
 #include <functional>
+#include <atomic>
 
 
 namespace realdds {
@@ -93,12 +94,17 @@ class dds_metadata_syncer
         return frame_holder( frame, _on_frame_release );
     }
 
+    void start() { _started = true; }
+    void stop() { _started = false; }
+
 private:
     // Call these under lock:
     void search_for_match( std::unique_lock< std::mutex > & );
     bool handle_match( std::unique_lock< std::mutex > & );
     bool handle_frame_without_metadata( std::unique_lock< std::mutex > & );
     bool drop_metadata( std::unique_lock< std::mutex > & );
+
+    std::atomic< bool > _started;
 };
 
 
diff --git a/third-party/realdds/py/pyrealdds.cpp b/third-party/realdds/py/pyrealdds.cpp
index 61e3fad4a4..f50e3bf2bf 100644
--- a/third-party/realdds/py/pyrealdds.cpp
+++ b/third-party/realdds/py/pyrealdds.cpp
@@ -1211,6 +1211,12 @@ PYBIND11_MODULE(NAME, m) {
         dds_metadata_syncer()
         {
             on_frame_release( frame_releaser );
+            start();
+        }
+
+        ~dds_metadata_syncer()
+        {
+            stop();
         }
 
         void enqueue_frame( key_type key, frame_type const & img )
diff --git a/third-party/realdds/src/dds-metadata-syncer.cpp b/third-party/realdds/src/dds-metadata-syncer.cpp
index 9a625cd0ee..1a5ddcfed6 100644
--- a/third-party/realdds/src/dds-metadata-syncer.cpp
+++ b/third-party/realdds/src/dds-metadata-syncer.cpp
@@ -112,7 +112,7 @@ bool dds_metadata_syncer::handle_match( std::unique_lock< std::mutex > & lock )
     _metadata_queue.pop_front();
     _frame_queue.pop_front();
 
-    if( _on_frame_ready )
+    if( _on_frame_ready && _started )
     {
         lock.unlock();
         _on_frame_ready( std::move( fh ), md );
@@ -132,7 +132,7 @@ bool dds_metadata_syncer::handle_frame_without_metadata( std::unique_lock< std::
     frame_holder fh = std::move( _frame_queue.front().second );
     _frame_queue.pop_front();
 
-    if( _on_frame_ready )
+    if( _on_frame_ready && _started )
     {
         lock.unlock();
         _on_frame_ready( std::move( fh ), metadata_type() );