diff --git a/apps/renderer.c b/apps/renderer.c
index 70e68c757d73716e18d248822b1f7dfc1b1f39d7..0e499863c948bc363a4c976c1ef5eff763a90252 100644
--- a/apps/renderer.c
+++ b/apps/renderer.c
@@ -1646,8 +1646,12 @@ int main(
 
     ObjectPositionBuffer mtdBuffer;
     outBuffer.pq_fact = &outBuffer.q_factor;
+#ifdef FIX_2257_INCR_GUARD_BITS
+    Word16 gd_bits = find_guard_bits( frameSize_smpls );
+#else
     Word16 subframe_len = (Word16) ( args.sampleRate / ( FRAMES_PER_SEC * MAX_PARAM_SPATIAL_SUBFRAMES ) );
     Word16 gd_bits = find_guard_bits( subframe_len );
+#endif
     Word16 prev_q_fact = Q11;
     while ( 1 )
     {
diff --git a/lib_com/fft_cldfb_fx.c b/lib_com/fft_cldfb_fx.c
index 230dd7ac59f6cff002e6b472a4aab281f04083f8..948854d36daa729a206cce3a49c751099d2fa712 100644
--- a/lib_com/fft_cldfb_fx.c
+++ b/lib_com/fft_cldfb_fx.c
@@ -19,7 +19,7 @@
    contributions.
 
    This software is provided "AS IS", without any express or implied warranties. The software is in the
-   development stage. It is intended exclusively for experts who have experience with such software and
+   development stage. It is int exclusively for experts who have experience with such software and
    solely for the purpose of inspection. All implied warranties of non-infringement, merchantability
    and fitness for a particular purpose are hereby disclaimed and excluded.
 
@@ -257,6 +257,17 @@ static void fft10_with_cmplx_data( cmplx *inp_data /*Qx*/ )
     cmplx x0, x1, x2, x3, x4, t;
     cmplx y[10];
 
+#ifdef FIX_ISSUE_2257_ADD_HEADROOM_IN_FFT10
+    Word16 headroom = L_norm_arr( (Word32 *) inp_data, 2 * 10 );
+    Word16 headroom_fix = ( headroom < 5 /* SCALEFACTOR10 */ ) ? ( 5 /* SCALEFACTOR10 */ - headroom ) : 0;
+    if ( headroom_fix != 0 )
+    {
+        for ( Word16 i = 0; i < 10; i++ )
+        {
+            inp_data[i] = CL_shr( inp_data[i], headroom_fix );
+        }
+    }
+#endif
     /* FOR i=0 */
     {
         x0 = CL_shr( inp_data[0], SCALEFACTOR10 );
@@ -343,6 +354,17 @@ static void fft10_with_cmplx_data( cmplx *inp_data /*Qx*/ )
 #ifdef WMOPS
     multiCounter[currCounter].CL_move += 10;
 #endif
+
+#ifdef FIX_ISSUE_2257_ADD_HEADROOM_IN_FFT10
+    if ( headroom_fix != 0 )
+    {
+        for ( Word16 i = 0; i < 10; i++ )
+        {
+            /* We want to get assertion in case of overflow, no saturation */
+            inp_data[i] = CL_shl( inp_data[i], headroom_fix );
+        }
+    }
+#endif
 }
 
 /**
diff --git a/lib_com/options.h b/lib_com/options.h
index a244037882e84546ecae3ae50084b5843083e95f..1f6f4cdcdde91d5709eee5e2ba223f91ca14ab77 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -131,6 +131,9 @@
 #define FIX_2252_LP_CNG_STARTS_SID                      /* VA: issues 2251 and 2252: fix LP CNG uninitialized value in bitstream that starts with an SID */
 #define FIX_1381_BWD                                    /* VA: issue 1381: apply no hysteresis in BWD at higher bitrates also in mono MASA and OMASA */
 #define FIX_2285_CODE_DECODER_INIT_BW                   /* VA: basop issue 2285: fix core-decoder initialization bandwidth */
+#define FIX_2257_INCR_GUARD_BITS                        /* FhG: take correct rendering frame-size into account for guard-bits calculation */
+#define FIX_ISSUE_2257_INCREASE_GUARD_BITS              /* FhG: (tri) adds +1 to result of find_guard_bits of len=320: 9 -> 10 */
+#define FIX_ISSUE_2257_ADD_HEADROOM_IN_FFT10            /* FhG: (tri) optional scale-down at entry and scale-up at end of FFT10, if headroom too small */
 #define FIX_2306_MISSING_UPDATE_LOWRATE_PITCH_GAIN      /* Dolby: Fix missing update of low-rate pitch gain in the S/M classifier */
 #define FIX_2297_SBA_SCALING_32KHZ                      /* VA: basop issue 2297: Fix scaling factor before the SBA decoder for output_Fs = 32 or 16 */
 
diff --git a/lib_rend/lib_rend_fx.c b/lib_rend/lib_rend_fx.c
old mode 100644
new mode 100755
index eaed6ebf5dc4edbc6380504fb6c90b5517bc20a1..c3dc51fa96da8e4dea77e8d44ff7297d84141f46
--- a/lib_rend/lib_rend_fx.c
+++ b/lib_rend/lib_rend_fx.c
@@ -7234,7 +7234,12 @@ static void renderIsmToMasa(
         q_min = s_min( q_min, L_norm_arr( tmpRendBuffer_fx[i], ismInput->base.inputBuffer.config.numSamplesPerChannel ) );
     }
 
+#ifdef FIX_ISSUE_2257_INCREASE_GUARD_BITS
+    guard_bits = add( 1, find_guarded_bits_fx( ismInput->base.inputBuffer.config.numSamplesPerChannel ) );
+#else
     guard_bits = find_guarded_bits_fx( ismInput->base.inputBuffer.config.numSamplesPerChannel );
+#endif
+
     q_min = sub( add( q_min, *outAudio.pq_fact ), guard_bits );
     q_diff = sub( q_min, *outAudio.pq_fact );