diff --git a/Marlin/Configuration.h b/Marlin/Configuration.h
index dc04fd2a0e..461101368e 100644
--- a/Marlin/Configuration.h
+++ b/Marlin/Configuration.h
@@ -717,6 +717,9 @@
  */
 #if ENABLED(MPCTEMP)
   #define MPC_AUTOTUNE                                // Include a method to do MPC auto-tuning (~6.3K bytes of flash)
+  #if ENABLED(MPC_AUTOTUNE)
+    //#define MPC_AUTOTUNE_DEBUG                      // Enable MPC debug logging (~870 bytes of flash)
+  #endif
   //#define MPC_EDIT_MENU                             // Add MPC editing to the "Advanced Settings" menu. (~1.3K bytes of flash)
   //#define MPC_AUTOTUNE_MENU                         // Add MPC auto-tuning to the "Advanced Settings" menu. (~350 bytes of flash)
 
diff --git a/Marlin/src/module/temperature.cpp b/Marlin/src/module/temperature.cpp
index 1b8ebeea69..f617d8391a 100644
--- a/Marlin/src/module/temperature.cpp
+++ b/Marlin/src/module/temperature.cpp
@@ -926,8 +926,6 @@ volatile bool Temperature::raw_temps_ready = false;
     #define SINGLEFAN 1
   #endif
 
-  #define DEBUG_MPC_AUTOTUNE 1
-
   millis_t Temperature::MPC_autotuner::curr_time_ms, Temperature::MPC_autotuner::next_report_ms;
 
   celsius_float_t Temperature::MPC_autotuner::temp_samples[16];
@@ -983,7 +981,7 @@ volatile bool Temperature::raw_temps_ready = false;
     }
     wait_for_heatup = false;
 
-    #if ENABLED(DEBUG_MPC_AUTOTUNE)
+    #if ENABLED(MPC_AUTOTUNE_DEBUG)
       SERIAL_ECHOLNPGM("MPC_autotuner::measure_ambient_temp() Completed");
       SERIAL_ECHOLNPGM("=====");
       SERIAL_ECHOLNPGM("ambient_temp ", get_ambient_temp());
@@ -1026,16 +1024,15 @@ volatile bool Temperature::raw_temps_ready = false;
 
           // Measure the rate of change of temperature, https://en.wikipedia.org/wiki/Symmetric_derivative
           const float h = MS_TO_SEC_PRECISE(test_interval_ms),
-              curr_rate = (temp_samples[2] - temp_samples[0]) / 2 * h;
+              curr_rate = (temp_samples[2] - temp_samples[0]) / 2 / h;
           if (curr_rate > rate_fastest) {
             // Update fastest values
             rate_fastest = curr_rate;
             temp_fastest = temp_samples[1];
-            time_fastest = get_elapsed_heating_time();
+            time_fastest = MS_TO_SEC_PRECISE(curr_time_ms - heat_start_time_ms - h);
           }
 
           next_test_time_ms += test_interval_ms;
-
         }
         else if (current_temp < 200.0f) {
           // Second regime (after 100deg) measure 3 points to determine asymptotic temperature
@@ -1052,7 +1049,6 @@ volatile bool Temperature::raw_temps_ready = false;
           temp_samples[sample_count++] = current_temp;
 
           next_test_time_ms += test_interval_ms * sample_distance;
-
         }
         else {
           // Third regime (after 200deg) finished gathering data so finish
@@ -1070,7 +1066,7 @@ volatile bool Temperature::raw_temps_ready = false;
     if (sample_count == 0) return FAILED;
     if (sample_count % 2 == 0) sample_count--;
 
-    #if ENABLED(DEBUG_MPC_AUTOTUNE)
+    #if ENABLED(MPC_AUTOTUNE_DEBUG)
       SERIAL_ECHOLNPGM("MPC_autotuner::measure_heatup() Completed");
       SERIAL_ECHOLNPGM("=====");
       SERIAL_ECHOLNPGM("t1_time ", t1_time);
@@ -1140,7 +1136,7 @@ volatile bool Temperature::raw_temps_ready = false;
     power_fan0 = total_energy_fan0 / MS_TO_SEC_PRECISE(test_duration);
     TERN_(HAS_FAN, power_fan255 = (total_energy_fan255 * 1000) / test_duration);
 
-    #if ENABLED(DEBUG_MPC_AUTOTUNE)
+    #if ENABLED(MPC_AUTOTUNE_DEBUG)
       SERIAL_ECHOLNPGM("MPC_autotuner::measure_transfer() Completed");
       SERIAL_ECHOLNPGM("=====");
       SERIAL_ECHOLNPGM("power_fan0 ", power_fan0);
@@ -1219,7 +1215,7 @@ volatile bool Temperature::raw_temps_ready = false;
     float asymp_temp = (t2 * t2 - t1 * t3) / (2 * t2 - t1 - t3),
           block_responsiveness = -log((t2 - asymp_temp) / (t1 - asymp_temp)) / tuner.get_sample_interval();
 
-    #if ENABLED(DEBUG_MPC_AUTOTUNE)
+    #if ENABLED(MPC_AUTOTUNE_DEBUG)
       SERIAL_ECHOLNPGM("asymp_temp ", asymp_temp);
       SERIAL_ECHOLNPGM("block_responsiveness ", p_float_t(block_responsiveness, 4));
     #endif
@@ -1235,15 +1231,18 @@ volatile bool Temperature::raw_temps_ready = false;
     }
 
     // If analytic tuning fails, fall back to differential tuning
-    if (tuning_type == AUTO) {
-      if (mpc.sensor_responsiveness <= 0 || mpc.block_heat_capacity <= 0)
+    if (tuning_type == AUTO && (mpc.sensor_responsiveness <= 0 || mpc.block_heat_capacity <= 0))
         tuning_type = FORCE_DIFFERENTIAL;
-    }
 
     if (tuning_type == FORCE_DIFFERENTIAL) {
+      #if ENABLED(MPC_AUTOTUNE_DEBUG)
+        SERIAL_ECHOLNPGM("rate_fastest ", tuner.get_rate_fastest());
+        SERIAL_ECHOLNPGM("time_fastest ", tuner.get_time_fastest());
+        SERIAL_ECHOLNPGM("temp_fastest ", tuner.get_temp_fastest());
+      #endif
       // Differential tuning
       mpc.block_heat_capacity = mpc.heater_power / tuner.get_rate_fastest();
-      mpc.sensor_responsiveness = tuner.get_rate_fastest() / (tuner.get_rate_fastest() * tuner.get_time_fastest() + tuner.get_ambient_temp() - tuner.get_time_fastest());
+      mpc.sensor_responsiveness = tuner.get_rate_fastest() / (tuner.get_rate_fastest() * tuner.get_time_fastest() + tuner.get_ambient_temp() - tuner.get_temp_fastest());
     }
 
     hotend.modeled_block_temp = asymp_temp + (tuner.get_ambient_temp() - asymp_temp) * exp(-block_responsiveness * tuner.get_elapsed_heating_time());
@@ -1269,7 +1268,7 @@ volatile bool Temperature::raw_temps_ready = false;
       asymp_temp = tuner.get_ambient_temp() + mpc.heater_power * (MPC_MAX) / 255 / mpc.ambient_xfer_coeff_fan0;
       block_responsiveness = -log((t2 - asymp_temp) / (t1 - asymp_temp)) / tuner.get_sample_interval();
 
-      #if ENABLED(DEBUG_MPC_AUTOTUNE)
+      #if ENABLED(MPC_AUTOTUNE_DEBUG)
         SERIAL_ECHOLNPGM("Refining estimates for:");
         SERIAL_ECHOLNPGM("asymp_temp ", asymp_temp);
         SERIAL_ECHOLNPGM("block_responsiveness ", p_float_t(block_responsiveness, 4));
@@ -1279,6 +1278,17 @@ volatile bool Temperature::raw_temps_ready = false;
       mpc.block_heat_capacity = mpc.ambient_xfer_coeff_fan0 / block_responsiveness;
       mpc.sensor_responsiveness = block_responsiveness / (1.0f - (tuner.get_ambient_temp() - asymp_temp) * exp(-block_responsiveness * tuner.get_sample_1_time()) / (t1 - asymp_temp));
 
+      // Check again: If analytic tuning fails, fall back to differential tuning
+      if (tuning_type == AUTO && (mpc.sensor_responsiveness <= 0 || mpc.block_heat_capacity <= 0)) {
+        #if ENABLED(MPC_AUTOTUNE_DEBUG)
+          SERIAL_ECHOLNPGM("rate_fastest ", tuner.get_rate_fastest());
+          SERIAL_ECHOLNPGM("time_fastest ", tuner.get_time_fastest());
+          SERIAL_ECHOLNPGM("temp_fastest ", tuner.get_temp_fastest());
+        #endif
+        tuning_type = FORCE_DIFFERENTIAL;
+        mpc.block_heat_capacity = mpc.heater_power / tuner.get_rate_fastest();
+        mpc.sensor_responsiveness = tuner.get_rate_fastest() / (tuner.get_rate_fastest() * tuner.get_time_fastest() + tuner.get_ambient_temp() - tuner.get_temp_fastest());
+      }
     }
 
     SERIAL_ECHOLNPGM(STR_MPC_AUTOTUNE_FINISHED);