diff --git a/lib_com/ivas_stat_com.h b/lib_com/ivas_stat_com.h
index 950e43a88efddccb73dcbee3b492183c89dc0cb3..c1e35d822c6d1482513a756a4fce6e3c4c26d04b 100644
--- a/lib_com/ivas_stat_com.h
+++ b/lib_com/ivas_stat_com.h
@@ -75,7 +75,9 @@ typedef struct
     int16_t ism_md_fec_cnt_enc;  /* counter of continuous frames where MD are not transmitted */
     int16_t ism_md_inc_diff_cnt; /* counter of continuous frames where MD are transmitted in inactive segments when MD significantly changes */
 #endif
-
+#ifdef FIX_435_ISM_MERGE_BUG
+    float last_true_radius; /* last true Q radius value */
+#endif
 } ISM_METADATA_FRAME, *ISM_METADATA_HANDLE;
 
 
diff --git a/lib_com/options.h b/lib_com/options.h
index d841a798e20bf1070ae3b84ec88d6d49ae03abef..c13b959e5fd33512a5e4f44c90e1d4bd6f2a81e9 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -172,6 +172,8 @@
 
 #define EUALER2QUAT_FIX                                 /*Dlb :fix for issue 430 issue in euler2quat, sign of quat y is inverted*/
 #define HR_METADATA                                     /* Nok: encode directional MASA metadata with more bits at 384k and 512k */
+
+#define FIX_435_ISM_MERGE_BUG                           /* Eri: Merge bug fix for ISM NULL metadata and tcx_only cases */
 /* ################## End DEVELOPMENT switches ######################### */
 /* clang-format on */
 #endif
diff --git a/lib_enc/ivas_ism_metadata_enc.c b/lib_enc/ivas_ism_metadata_enc.c
index e9e40a574c92de18d8412efd64ff842f1755e1f7..a4678d6bbb1dcba739f6876f2e81f806d778c94b 100644
--- a/lib_enc/ivas_ism_metadata_enc.c
+++ b/lib_enc/ivas_ism_metadata_enc.c
@@ -61,7 +61,9 @@
 #define ISM_MD_INC_DIFF_CNT_MAX 6
 #define ISM_MD_FEC_CNT_MAX      25
 #endif
-
+#ifdef FIX_435_ISM_MERGE_BUG
+#define ISM_MD_RAD_FEC_DIFF 1
+#endif
 #define INTER_OBJECT_PARAM_CHECK ( ( ISM_FEC_MAX / 2 ) - 2 ) /* note: constant must be less than (ISM_FEC_MAX / number of coded parameters)  */
 
 
@@ -221,36 +223,49 @@ ivas_error ivas_ism_metadata_enc(
         }
         else if ( ism_mode == ISM_MODE_DISC )
         {
+#ifdef FIX_435_ISM_MERGE_BUG
+            if ( hIsmMeta[ch]->ism_metadata_flag == 1 )
+            {
+                /* In case of low level noise for low bitrate inactive frames, do not sent metadata */
+                hIsmMeta[ch]->ism_metadata_flag = localVAD[ch] || hSCE[ch]->hCoreCoder[0]->lp_noise > 10 || hSCE[ch]->hCoreCoder[0]->tcxonly;
+#else
             hIsmMeta[ch]->ism_metadata_flag = localVAD[ch] || hSCE[ch]->hCoreCoder[0]->lp_noise > 10;
-
+#endif
 #ifdef FIX_387_ISM_MD_FEC
-            /* in inactive frames, send MD 1) in ISM_MD_INC_DIFF_CNT_MAX consecutive frames when MD significantly change, 2) at least every ISM_MD_FEC_DIFF frames */
-            if ( hIsmMeta[ch]->ism_metadata_flag == 0 )
-            {
-                if ( ( fabsf( hIsmMeta[ch]->azimuth - hIsmMeta[ch]->last_true_azimuth ) > ISM_MD_FEC_DIFF ) ||
-                     ( fabsf( hIsmMeta[ch]->elevation - hIsmMeta[ch]->last_true_elevation ) > ISM_MD_FEC_DIFF ) )
+                /* in inactive frames, send MD 1) in ISM_MD_INC_DIFF_CNT_MAX consecutive frames when MD significantly change, 2) at least every ISM_MD_FEC_DIFF frames */
+                if ( hIsmMeta[ch]->ism_metadata_flag == 0 )
                 {
-                    hIsmMeta[ch]->ism_metadata_flag = 1;
-                    hIsmMeta[ch]->ism_md_inc_diff_cnt = 0;
-                }
-                else if ( hIsmMeta[ch]->ism_md_inc_diff_cnt < ISM_MD_INC_DIFF_CNT_MAX )
-                {
-                    hIsmMeta[ch]->ism_metadata_flag = 1;
-
-                    if ( hIsmMeta[ch]->ism_md_inc_diff_cnt % 2 == 0 )
+                    if ( ( fabsf( hIsmMeta[ch]->azimuth - hIsmMeta[ch]->last_true_azimuth ) > ISM_MD_FEC_DIFF ) ||
+                         ( fabsf( hIsmMeta[ch]->elevation - hIsmMeta[ch]->last_true_elevation ) > ISM_MD_FEC_DIFF )
+#ifdef FIX_435_ISM_MERGE_BUG
+                         || ( fabsf( hIsmMeta[ch]->radius - hIsmMeta[ch]->last_true_radius ) > ISM_MD_RAD_FEC_DIFF )
+#endif
+                    )
                     {
-                        hIsmMeta[ch]->position_angle.angle1_diff_cnt = ISM_FEC_MAX;
+                        hIsmMeta[ch]->ism_metadata_flag = 1;
+                        hIsmMeta[ch]->ism_md_inc_diff_cnt = 0;
                     }
-                    else
+                    else if ( hIsmMeta[ch]->ism_md_inc_diff_cnt < ISM_MD_INC_DIFF_CNT_MAX )
                     {
-                        hIsmMeta[ch]->position_angle.angle2_diff_cnt = ISM_FEC_MAX;
+                        hIsmMeta[ch]->ism_metadata_flag = 1;
+
+                        if ( hIsmMeta[ch]->ism_md_inc_diff_cnt % 2 == 0 )
+                        {
+                            hIsmMeta[ch]->position_angle.angle1_diff_cnt = ISM_FEC_MAX;
+                        }
+                        else
+                        {
+                            hIsmMeta[ch]->position_angle.angle2_diff_cnt = ISM_FEC_MAX;
+                        }
+                    }
+                    else if ( hIsmMeta[ch]->ism_md_fec_cnt_enc == ISM_MD_FEC_CNT_MAX )
+                    {
+                        hIsmMeta[ch]->ism_metadata_flag = 1;
+                        hIsmMeta[ch]->position_angle.angle1_diff_cnt = ISM_FEC_MAX;
                     }
                 }
-                else if ( hIsmMeta[ch]->ism_md_fec_cnt_enc == ISM_MD_FEC_CNT_MAX )
-                {
-                    hIsmMeta[ch]->ism_metadata_flag = 1;
-                    hIsmMeta[ch]->position_angle.angle1_diff_cnt = ISM_FEC_MAX;
-                }
+#endif
+#ifdef FIX_435_ISM_MERGE_BUG
             }
 #endif
         }
@@ -369,6 +384,9 @@ ivas_error ivas_ism_metadata_enc(
                 /* Updates */
                 hIsmMeta[ch]->last_true_azimuth = hIsmMeta[ch]->azimuth;
                 hIsmMeta[ch]->last_true_elevation = hIsmMeta[ch]->elevation;
+#endif
+#ifdef FIX_435_ISM_MERGE_BUG
+                hIsmMeta[ch]->last_true_radius = hIsmMeta[ch]->radius;
 #endif
             }
         }
@@ -610,6 +628,9 @@ ivas_error ivas_ism_metadata_enc_create(
         st_ivas->hIsmMetaData[ch]->last_true_elevation = 0.0f;
         st_ivas->hIsmMetaData[ch]->ism_md_fec_cnt_enc = 0;
         st_ivas->hIsmMetaData[ch]->ism_md_inc_diff_cnt = ISM_MD_INC_DIFF_CNT_MAX;
+#endif
+#ifdef FIX_435_ISM_MERGE_BUG
+        st_ivas->hIsmMetaData[ch]->last_true_radius = 1.0f;
 #endif
     }