diff --git a/lib_enc/ivas_mdct_core_enc_fx.c b/lib_enc/ivas_mdct_core_enc_fx.c
index 9027b26691e73a2c8e3be89e83311152b20adb12..9f674473ecec6f4e2b009791b04c1debadaf6f7b 100644
--- a/lib_enc/ivas_mdct_core_enc_fx.c
+++ b/lib_enc/ivas_mdct_core_enc_fx.c
@@ -1556,27 +1556,30 @@ void ivas_mdct_core_whitening_enc_fx(
                 }
                 IF( EQ_16( hTcxEnc0->transform_type[n], TCX_5 ) )
                 {
-                    Word16 length;
+                    Word16 length, len_sbfr;
                     const Word16 tcx5SizeFB = sts[1]->hTcxCfg->tcx5SizeFB;
                     move16();
                     /* length = max(nSampCore / (2 * NB_DIV), L_subframeTCX / (2 * NB_DIV),  NB_DIV = 2 */
                     length = shr( s_max( nSampCore, L_subframeTCX ), 2 );
+                    len_sbfr = shr( hTcxEnc0->L_frameTCX, shift );
+                    assert( hTcxEnc0->L_frameTCX == hTcxEnc1->L_frameTCX );
                     exp_max = s_max( hTcxEnc0->spectrum_e[n], hTcxEnc1->spectrum_e[n] );
                     exp_max = s_max( exp_max, mdst_spectrum_e[0][n] );
                     exp_max = s_max( exp_max, mdst_spectrum_e[1][n] );
 
                     // calculate the headroom available
-                    exp_com = s_min( L_norm_arr( hTcxEnc1->spectrum_fx[n], length ), L_norm_arr( hTcxEnc0->spectrum_fx[n], length ) );
-                    exp_com = s_min( exp_com, L_norm_arr( mdst_spectrum_fx[0][n], length ) );
-                    exp_com = s_min( exp_com, L_norm_arr( mdst_spectrum_fx[1][n], length ) );
+                    exp_com = s_min( L_norm_arr( hTcxEnc1->spectrum_fx[n], len_sbfr ), L_norm_arr( hTcxEnc0->spectrum_fx[n], len_sbfr ) );
+                    exp_com = s_min( exp_com, L_norm_arr( mdst_spectrum_fx[0][n], len_sbfr ) );
+                    exp_com = s_min( exp_com, L_norm_arr( mdst_spectrum_fx[1][n], len_sbfr ) );
 
                     q_com = sub( s_min( Q31, add( sub( Q31, exp_max ), exp_com ) ), 6 ); // 6 guarded bits
+                    q_com = s_max( q_com, 9 );                                           // Keep the Q-factor at least 9 to avoid precision loss inside enc_ste_pre_mdct.
                     exp_com = sub( Q31, q_com );
 
-                    Scale_sig32( hTcxEnc0->spectrum_fx[n], shr( hTcxEnc0->L_frameTCX, shift ) /* hTcxEnc0->L_frameTCX/nSubframes */, sub( hTcxEnc0->spectrum_e[n], exp_com ) ); // hTcxEnc0->spectrum_e
-                    Scale_sig32( hTcxEnc1->spectrum_fx[n], shr( hTcxEnc1->L_frameTCX, shift ) /* hTcxEnc1->L_frameTCX/nSubframes */, sub( hTcxEnc1->spectrum_e[n], exp_com ) ); // hTcxEnc1->spectrum_e
-                    Scale_sig32( mdst_spectrum_fx[0][n], shr( hTcxEnc0->L_frameTCX, shift ) /* hTcxEnc0->L_frameTCX/nSubframes */, sub( mdst_spectrum_e[0][n], exp_com ) );     // mdst_spectrum_e
-                    Scale_sig32( mdst_spectrum_fx[1][n], shr( hTcxEnc1->L_frameTCX, shift ) /* hTcxEnc1->L_frameTCX/nSubframes */, sub( mdst_spectrum_e[1][n], exp_com ) );     // mdst_spectrum_e
+                    scale_sig32( hTcxEnc0->spectrum_fx[n], len_sbfr /* hTcxEnc0->L_frameTCX/nSubframes */, sub( hTcxEnc0->spectrum_e[n], exp_com ) ); // hTcxEnc0->spectrum_e
+                    scale_sig32( hTcxEnc1->spectrum_fx[n], len_sbfr /* hTcxEnc1->L_frameTCX/nSubframes */, sub( hTcxEnc1->spectrum_e[n], exp_com ) ); // hTcxEnc1->spectrum_e
+                    scale_sig32( mdst_spectrum_fx[0][n], len_sbfr /* hTcxEnc0->L_frameTCX/nSubframes */, sub( mdst_spectrum_e[0][n], exp_com ) );     // mdst_spectrum_e
+                    scale_sig32( mdst_spectrum_fx[1][n], len_sbfr /* hTcxEnc1->L_frameTCX/nSubframes */, sub( mdst_spectrum_e[1][n], exp_com ) );     // mdst_spectrum_e
 
                     Word16 q_com_orig = q_com;
                     move16();
@@ -1600,17 +1603,18 @@ void ivas_mdct_core_whitening_enc_fx(
                     exp_max = sub( Q31, q_com );
                     move16();
 
-                    exp_com = s_min( L_norm_arr( hTcxEnc1->spectrum_fx[n], shr( hTcxEnc1->L_frameTCX, shift ) /* hTcxEnc1->L_frameTCX/nSubframes */ ), L_norm_arr( hTcxEnc0->spectrum_fx[n], shr( hTcxEnc0->L_frameTCX, shift ) /* hTcxEnc0->L_frameTCX/nSubframes */ ) );
-                    exp_com = s_min( exp_com, L_norm_arr( mdst_spectrum_fx[0][n], shr( hTcxEnc0->L_frameTCX, shift ) /* hTcxEnc0->L_frameTCX/nSubframes */ ) );
-                    exp_com = s_min( exp_com, L_norm_arr( mdst_spectrum_fx[1][n], shr( hTcxEnc1->L_frameTCX, shift ) /* hTcxEnc1->L_frameTCX/nSubframes */ ) );
+                    exp_com = s_min( L_norm_arr( hTcxEnc1->spectrum_fx[n], len_sbfr /* hTcxEnc1->L_frameTCX/nSubframes */ ), L_norm_arr( hTcxEnc0->spectrum_fx[n], len_sbfr /* hTcxEnc0->L_frameTCX/nSubframes */ ) );
+                    exp_com = s_min( exp_com, L_norm_arr( mdst_spectrum_fx[0][n], len_sbfr /* hTcxEnc0->L_frameTCX/nSubframes */ ) );
+                    exp_com = s_min( exp_com, L_norm_arr( mdst_spectrum_fx[1][n], len_sbfr /* hTcxEnc1->L_frameTCX/nSubframes */ ) );
 
                     q_com = sub( s_min( Q31, add( q_com, exp_com ) ), 6 );
+                    q_com = s_max( q_com, 9 ); // Keep the Q-factor at least 9 to avoid precision loss inside enc_ste_pre_mdct.
                     exp_com = sub( Q31, q_com );
 
-                    Scale_sig32( hTcxEnc0->spectrum_fx[n], shr( hTcxEnc0->L_frameTCX, shift ) /* hTcxEnc0->L_frameTCX/nSubframes */, sub( exp_max, exp_com ) ); // exp_max
-                    Scale_sig32( hTcxEnc1->spectrum_fx[n], shr( hTcxEnc1->L_frameTCX, shift ) /* hTcxEnc1->L_frameTCX/nSubframes */, sub( exp_max, exp_com ) ); // exp_max
-                    Scale_sig32( mdst_spectrum_fx[0][n], shr( hTcxEnc0->L_frameTCX, shift ) /* hTcxEnc0->L_frameTCX/nSubframes */, sub( exp_max, exp_com ) );   // exp_max
-                    Scale_sig32( mdst_spectrum_fx[1][n], shr( hTcxEnc1->L_frameTCX, shift ) /* hTcxEnc1->L_frameTCX/nSubframes */, sub( exp_max, exp_com ) );   // exp_max
+                    scale_sig32( hTcxEnc0->spectrum_fx[n], len_sbfr /* hTcxEnc0->L_frameTCX/nSubframes */, sub( exp_max, exp_com ) ); // exp_max
+                    scale_sig32( hTcxEnc1->spectrum_fx[n], len_sbfr /* hTcxEnc1->L_frameTCX/nSubframes */, sub( exp_max, exp_com ) ); // exp_max
+                    scale_sig32( mdst_spectrum_fx[0][n], len_sbfr /* hTcxEnc0->L_frameTCX/nSubframes */, sub( exp_max, exp_com ) );   // exp_max
+                    scale_sig32( mdst_spectrum_fx[1][n], len_sbfr /* hTcxEnc1->L_frameTCX/nSubframes */, sub( exp_max, exp_com ) );   // exp_max
 
                     q_com_orig = q_com;
                     move16();