diff --git a/ql-application/threadx/interface/custom_app/vad_det.c b/ql-application/threadx/interface/custom_app/vad_det.c
index 946ede6..45508a8 100644
--- a/ql-application/threadx/interface/custom_app/vad_det.c
+++ b/ql-application/threadx/interface/custom_app/vad_det.c
@@ -420,17 +420,21 @@ void vad_audio_process(void) {
 						#endif
 						
 	                        first_sound_detected = true;
-						{
-							size_t first = (vad_preroll_next + VAD_PREROLL_FRAMES - vad_preroll_count) % VAD_PREROLL_FRAMES;
-							size_t n;
-							for (n = 0; n < vad_preroll_count; n++) {
-								size_t frame_index = (first + n) % VAD_PREROLL_FRAMES;
-								if (hal_os_rb_write(ring_sender, vad_preroll[frame_index], VAD_FRAME_BYTES, 25) > 0) {
-									ql_rtos_semaphore_release(sender_sem);
-								}
-							}
-							vad_preroll_count = 0;
-						}
+						{
+							size_t first = (vad_preroll_next + VAD_PREROLL_FRAMES - vad_preroll_count) % VAD_PREROLL_FRAMES;
+							size_t n;
+							int preroll_queued = 0;
+							for (n = 0; n < vad_preroll_count; n++) {
+								size_t frame_index = (first + n) % VAD_PREROLL_FRAMES;
+								if (hal_os_rb_write(ring_sender, vad_preroll[frame_index], VAD_FRAME_BYTES, 25) > 0) {
+									preroll_queued = 1;
+								}
+							}
+							if (preroll_queued) {
+								ql_rtos_semaphore_release(sender_sem);
+							}
+							vad_preroll_count = 0;
+						}
 	                        set_state(STATE_RECORDING_ACTIVE);
                         printf("First speech confirmed by FVAD (continuous %d frames)", SPEECH_DETECT_THRESHOLD);
                     }
diff --git a/ql-application/threadx/interface/custom_app/ws_talkingq.c b/ql-application/threadx/interface/custom_app/ws_talkingq.c
index fb23d05..e792f93 100644
--- a/ql-application/threadx/interface/custom_app/ws_talkingq.c
+++ b/ql-application/threadx/interface/custom_app/ws_talkingq.c
@@ -1365,9 +1365,17 @@ sender_loop:
 				continue;
 			}
 
-			if(!app_get_data_call_net_status()) continue;
-
-			if(shine_init==0){
+			if(!app_get_data_call_net_status()) continue;
+
+			/* One recording can release the semaphore many times while the sender
+			 * drains the ring buffer.  A stale token must never create an empty
+			 * session after the previous encoder has already been closed. */
+			left = rb_get_space_used(ring_sender);
+			if(shine_init == 0 && left <= 0){
+				continue;
+			}
+
+			if(shine_init==0){
 				shine_set_config_mpeg_defaults(&(sh_config.mpeg)); //--init sh_config struct
 				sh_config.wave.channels=PCM_MONO; //PCM_STEREO;//PCM_MONO;
 				sh_config.wave.samplerate=16000;//valid samplerates: 44100,48000,32000,22050,24000,16000,11025,12000,8000
@@ -1417,10 +1425,13 @@ sender_loop:
 					sh_shine = NULL;
 				}
 
-				shine_init = 0;
-				
-				audio_packet_type = 0;
-			}
+				shine_init = 0;
+
+				audio_packet_type = 0;
+				/* Discard semaphore tokens already represented by the PCM that this
+				 * session drained.  Recording has stopped, so no new frames race here. */
+				while(ql_rtos_semaphore_wait(sender_sem, 0) == 0) {}
+			}
 	}
 }