diff --git a/Marlin/MarlinSerial.cpp b/Marlin/MarlinSerial.cpp
index bf7675426d..d0921f4704 100644
--- a/Marlin/MarlinSerial.cpp
+++ b/Marlin/MarlinSerial.cpp
@@ -542,6 +542,8 @@ MarlinSerial customizedSerial;
             case state_M410:
               quickstop_stepper();
               break;
+            default:
+              break;
           }
           state = state_RESET;
         }
diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index 31545ab478..e9bb9c3dcd 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -5965,7 +5965,7 @@ void quickstop_stepper() {
    * Use either 'M421 X<linear> Y<linear> Z<linear>' or 'M421 I<xindex> J<yindex> Z<linear>'
    */
   inline void gcode_M421() {
-    int8_t px, py;
+    int8_t px = 0, py = 0;
     float z = 0;
     bool hasX, hasY, hasZ, hasI, hasJ;
     if ((hasX = code_seen('X'))) px = mbl.probe_index_x(code_value_axis_units(X_AXIS));
@@ -6210,7 +6210,9 @@ inline void gcode_M503() {
     disable_e3();
     delay(100);
 
-    millis_t next_tick = 0;
+    #if HAS_BUZZER
+      millis_t next_tick = 0;
+    #endif
 
     // Wait for filament insert by user and press button
     lcd_filament_change_show_message(FILAMENT_CHANGE_MESSAGE_INSERT);
diff --git a/Marlin/planner.cpp b/Marlin/planner.cpp
index b742dfe6ea..00ea8540ce 100644
--- a/Marlin/planner.cpp
+++ b/Marlin/planner.cpp
@@ -397,8 +397,12 @@ void Planner::check_axes_activity() {
   #endif
 
   #if ENABLED(BARICUDA)
-    unsigned char tail_valve_pressure = baricuda_valve_pressure,
-                  tail_e_to_p_pressure = baricuda_e_to_p_pressure;
+    #if HAS_HEATER_1
+      unsigned char tail_valve_pressure = baricuda_valve_pressure;
+    #endif
+    #if HAS_HEATER_2
+      unsigned char tail_e_to_p_pressure = baricuda_e_to_p_pressure;
+    #endif
   #endif
 
   if (blocks_queued()) {
@@ -411,8 +415,12 @@ void Planner::check_axes_activity() {
 
     #if ENABLED(BARICUDA)
       block = &block_buffer[block_buffer_tail];
-      tail_valve_pressure = block->valve_pressure;
-      tail_e_to_p_pressure = block->e_to_p_pressure;
+      #if HAS_HEATER_1
+        tail_valve_pressure = block->valve_pressure;
+      #endif
+      #if HAS_HEATER_2
+        tail_e_to_p_pressure = block->e_to_p_pressure;
+      #endif
     #endif
 
     for (uint8_t b = block_buffer_tail; b != block_buffer_head; b = next_block_index(b)) {
diff --git a/Marlin/ultralcd.cpp b/Marlin/ultralcd.cpp
index ae24461fc3..d2b349881e 100755
--- a/Marlin/ultralcd.cpp
+++ b/Marlin/ultralcd.cpp
@@ -230,7 +230,7 @@ uint8_t lcdDrawUpdate = LCDVIEW_CLEAR_CALL_REDRAW; // Set when the LCD needs to
     for (uint8_t _drawLineNr = 0; _drawLineNr < LCD_HEIGHT; _drawLineNr++, _lineNr++) { \
       _menuItemNr = 0;
 
-  #define START_SCREEN() _START_SCREEN(0)
+  #define START_SCREEN() _START_SCREEN(NOOP)
 
   /**
    * START_MENU generates the init code for a menu function