diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index fa7c9b1cd..0ad7e3656 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -3817,7 +3817,7 @@ inline void gcode_G28() {
     SERIAL_PROTOCOLPGM("Z offset: "); SERIAL_PROTOCOL_F(mbl.z_offset, 5);
     SERIAL_PROTOCOLLNPGM("\nMeasured points:");
     print_2d_array(GRID_MAX_POINTS_X, GRID_MAX_POINTS_Y, 5,
-      [](const uint8_t ix, const uint8_t iy) { return mbl.z_values[iy][ix]; }
+      [](const uint8_t ix, const uint8_t iy) { return mbl.z_values[ix][iy]; }
     );
   }
 
@@ -3948,7 +3948,7 @@ inline void gcode_G28() {
         }
 
         if (code_seen('Z')) {
-          mbl.z_values[py][px] = code_value_axis_units(Z_AXIS);
+          mbl.z_values[px][py] = code_value_axis_units(Z_AXIS);
         }
         else {
           SERIAL_CHAR('Z'); say_not_entered();
@@ -7844,7 +7844,7 @@ void quickstop_stepper() {
     }
   }
 
-#elif ENABLED(AUTO_BED_LEVELING_BILINEAR)
+#elif ENABLED(AUTO_BED_LEVELING_BILINEAR) || ENABLED(AUTO_BED_LEVELING_UBL)
 
   /**
    * M421: Set a single Mesh Bed Leveling Z coordinate
@@ -7861,9 +7861,13 @@ void quickstop_stepper() {
 
     if (hasI && hasJ && hasZ) {
       if (WITHIN(px, 0, GRID_MAX_POINTS_X - 1) && WITHIN(py, 0, GRID_MAX_POINTS_X - 1)) {
-        bed_level_grid[px][py] = z;
-        #if ENABLED(ABL_BILINEAR_SUBDIVISION)
-          bed_level_virt_interpolate();
+        #if ENABLED(AUTO_BED_LEVELING_UBL)
+          ubl.z_values[px][py] = z;
+        #else
+          bed_level_grid[px][py] = z;
+          #if ENABLED(ABL_BILINEAR_SUBDIVISION)
+            bed_level_virt_interpolate();
+          #endif
         #endif
       }
       else {
@@ -7876,34 +7880,7 @@ void quickstop_stepper() {
       SERIAL_ERRORLNPGM(MSG_ERR_M421_PARAMETERS);
     }
   }
-#elif ENABLED(AUTO_BED_LEVELING_UBL)
-  /**
-   * M421: Set a single Mesh Bed Leveling Z coordinate
-   *
-   *   M421 I<xindex> J<yindex> Z<linear>
-   */
-  inline void gcode_M421() {
-    int8_t px = 0, py = 0;
-    float z = 0;
-    bool hasI, hasJ, hasZ;
-    if ((hasI = code_seen('I'))) px = code_value_axis_units(X_AXIS);
-    if ((hasJ = code_seen('J'))) py = code_value_axis_units(Y_AXIS);
-    if ((hasZ = code_seen('Z'))) z = code_value_axis_units(Z_AXIS);
 
-    if (hasI && hasJ && hasZ) {
-      if (WITHIN(px, 0, GRID_MAX_POINTS_Y - 1) && WITHIN(py, 0, GRID_MAX_POINTS_Y - 1)) {
-        ubl.z_values[px][py] = z;
-      }
-      else {
-        SERIAL_ERROR_START;
-        SERIAL_ERRORLNPGM(MSG_ERR_MESH_XY);
-      }
-    }
-    else {
-      SERIAL_ERROR_START;
-      SERIAL_ERRORLNPGM(MSG_ERR_M421_PARAMETERS);
-    }
-  }
 #endif
 
 #if DISABLED(NO_WORKSPACE_OFFSETS)
diff --git a/Marlin/configuration_store.cpp b/Marlin/configuration_store.cpp
index a5c47dc1d..9ada6f536 100644
--- a/Marlin/configuration_store.cpp
+++ b/Marlin/configuration_store.cpp
@@ -36,7 +36,7 @@
  *
  */
 
-#define EEPROM_VERSION "V33"
+#define EEPROM_VERSION "V34"
 
 // Change EEPROM version if these are changed:
 #define EEPROM_OFFSET 100
@@ -1267,13 +1267,13 @@ void MarlinSettings::reset() {
         SERIAL_ECHOLNPAIR(" Z", planner.z_fade_height);
       #endif
       SERIAL_EOL;
-      for (uint8_t py = 1; py <= GRID_MAX_POINTS_Y; py++) {
-        for (uint8_t px = 1; px <= GRID_MAX_POINTS_X; px++) {
+      for (uint8_t py = 0; py < GRID_MAX_POINTS_Y; py++) {
+        for (uint8_t px = 0; px < GRID_MAX_POINTS_X; px++) {
           CONFIG_ECHO_START;
-          SERIAL_ECHOPAIR("  G29 S3 X", (int)px);
-          SERIAL_ECHOPAIR(" Y", (int)py);
+          SERIAL_ECHOPAIR("  G29 S3 X", (int)px + 1);
+          SERIAL_ECHOPAIR(" Y", (int)py + 1);
           SERIAL_ECHOPGM(" Z");
-          SERIAL_PROTOCOL_F(mbl.z_values[py-1][px-1], 5);
+          SERIAL_PROTOCOL_F(mbl.z_values[px][py], 5);
           SERIAL_EOL;
         }
       }
diff --git a/Marlin/mesh_bed_leveling.cpp b/Marlin/mesh_bed_leveling.cpp
index ef7e4ff38..08fdd3f86 100644
--- a/Marlin/mesh_bed_leveling.cpp
+++ b/Marlin/mesh_bed_leveling.cpp
@@ -29,7 +29,7 @@
   uint8_t mesh_bed_leveling::status;
 
   float mesh_bed_leveling::z_offset,
-        mesh_bed_leveling::z_values[GRID_MAX_POINTS_Y][GRID_MAX_POINTS_X],
+        mesh_bed_leveling::z_values[GRID_MAX_POINTS_X][GRID_MAX_POINTS_Y],
         mesh_bed_leveling::index_to_xpos[GRID_MAX_POINTS_X],
         mesh_bed_leveling::index_to_ypos[GRID_MAX_POINTS_Y];
 
diff --git a/Marlin/mesh_bed_leveling.h b/Marlin/mesh_bed_leveling.h
index 9d3bd9e9f..71274eeea 100644
--- a/Marlin/mesh_bed_leveling.h
+++ b/Marlin/mesh_bed_leveling.h
@@ -47,7 +47,7 @@
   public:
     static uint8_t status; // Has Mesh and Is Active bits
     static float z_offset,
-                 z_values[GRID_MAX_POINTS_Y][GRID_MAX_POINTS_X],
+                 z_values[GRID_MAX_POINTS_X][GRID_MAX_POINTS_Y],
                  index_to_xpos[GRID_MAX_POINTS_X],
                  index_to_ypos[GRID_MAX_POINTS_Y];
 
@@ -55,7 +55,7 @@
 
     static void reset();
 
-    static void set_z(const int8_t px, const int8_t py, const float &z) { z_values[py][px] = z; }
+    static void set_z(const int8_t px, const int8_t py, const float &z) { z_values[px][py] = z; }
 
     static bool active()                       { return TEST(status, MBL_STATUS_ACTIVE_BIT); }
     static void set_active(const bool onOff)   { onOff ? SBI(status, MBL_STATUS_ACTIVE_BIT) : CBI(status, MBL_STATUS_ACTIVE_BIT); }
@@ -108,8 +108,8 @@
       #endif
     ) {
       const int8_t cx = cell_index_x(x0), cy = cell_index_y(y0);
-      const float z1 = calc_z0(x0, index_to_xpos[cx], z_values[cy][cx], index_to_xpos[cx + 1], z_values[cy][cx + 1]),
-                  z2 = calc_z0(x0, index_to_xpos[cx], z_values[cy + 1][cx], index_to_xpos[cx + 1], z_values[cy + 1][cx + 1]),
+      const float z1 = calc_z0(x0, index_to_xpos[cx], z_values[cx][cy], index_to_xpos[cx + 1], z_values[cx + 1][cy]),
+                  z2 = calc_z0(x0, index_to_xpos[cx], z_values[cx][cy + 1], index_to_xpos[cx + 1], z_values[cx + 1][cy + 1]),
                   z0 = calc_z0(y0, index_to_ypos[cy], z1, index_to_ypos[cy + 1], z2);
 
       return z_offset + z0