diff --git a/lib_com/options.h b/lib_com/options.h
index 9089edfddc71d7c9fbfffb7874abc0428787cacf..3c9467e8ac18521ea5d4e8f36196240860eda83f 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -176,6 +176,7 @@
 #define NONBE_1122_KEEP_EVS_MODE_UNCHANGED              /* FhG: Disables fix for issue 1122 in EVS mode to keep BE tests green. This switch should be removed once the 1122 fix is added to EVS via a CR.  */
 #define NONBE_FIX_1337_MISSING_DIRECTIVITY_DISTATT_EXTREND /* Eri: issue 1337: Missing directivity setting and distance attenuation in external renderer IVAS_rend */
 #define NONBE_1329_FIX_OSBA_CRASH                       /* FhG: issue 1329: prevent assert when bit budget is low*/
+#define NONBE_FIX_TCX5_INTERLEAVING_FOR_FS_IN_UNEQUAL_FS_OUT /* FhG: apply correct TCX5 grouping/interleaving when input_fs != output_fs */
 #define NONBE_1339_FIXOSBA_EXT_LOUDNESS                 /* FhG: issue 1339: apply scaling with EXT output in OSBA high-BR mode */
 
 /* ##################### End NON-BE switches ########################### */
diff --git a/lib_dec/dec_tcx.c b/lib_dec/dec_tcx.c
index c371d0c9f9000b0cf083ce39370cc7c32f475bfe..0fb28ddb2d27b73558c6944576de9c1cf9112bee 100644
--- a/lib_dec/dec_tcx.c
+++ b/lib_dec/dec_tcx.c
@@ -1506,7 +1506,11 @@ void decoder_tcx_tns(
             hTcxCfg->tcx_last_overlap_mode = hTcxCfg->tcx_curr_overlap_mode;
         }
 
+#ifdef NONBE_FIX_TCX5_INTERLEAVING_FOR_FS_IN_UNEQUAL_FS_OUT
+        if ( ( hTcxCfg->fIsTNSAllowed && fUseTns != 0 && bfi != 1 && whitenedDomain ) || ( L_spec > L_frameTCX ) )
+#else
         if ( ( hTcxCfg->fIsTNSAllowed && fUseTns != 0 && bfi != 1 ) || ( L_spec > L_frameTCX ) )
+#endif
         {
             L = L_spec;
         }
@@ -1548,7 +1552,11 @@ void decoder_tcx_tns(
 
         if ( ( L_frame == st->L_frame >> 1 ) && st->tcxonly && isTCX5 )
         {
+#ifdef NONBE_FIX_TCX5_INTERLEAVING_FOR_FS_IN_UNEQUAL_FS_OUT
+            if ( st->element_mode == EVS_MONO || ( L_spec < L_frameTCX && !whitenedDomain ) ) /* todo: this is temporary to maintain EVS BE, this is a bug and should be fixed also for EVS (see issue 13) */
+#else
             if ( st->element_mode == EVS_MONO || L_spec < L_frameTCX ) /* todo: this is temporary to maintain EVS BE, this is a bug and should be fixed also for EVS (see issue 13) */
+#endif
             {
                 tcx5TnsUngrouping( L_frameTCX >> 1, hTcxCfg->tnsConfig[0][0].iFilterBorders[0] >> 1, x, DEC );
             }