diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index 113432403..da1739b22 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -5559,7 +5559,7 @@ void home_all_axes() { gcode_G28(true); }
             N++;
           }
         zero_std_dev_old = zero_std_dev;
-        zero_std_dev = round(sqrt(S2 / N) * 1000.0) / 1000.0 + 0.00001;
+        zero_std_dev = round(SQRT(S2 / N) * 1000.0) / 1000.0 + 0.00001;
 
         // Solve matrices
 
@@ -7745,16 +7745,17 @@ inline void gcode_M110() {
  * M111: Set the debug level
  */
 inline void gcode_M111() {
-  marlin_debug_flags = parser.byteval('S', (uint8_t)DEBUG_NONE);
+  if (parser.seen('S')) marlin_debug_flags = parser.byteval('S');
 
-  const static char str_debug_1[] PROGMEM = MSG_DEBUG_ECHO;
-  const static char str_debug_2[] PROGMEM = MSG_DEBUG_INFO;
-  const static char str_debug_4[] PROGMEM = MSG_DEBUG_ERRORS;
-  const static char str_debug_8[] PROGMEM = MSG_DEBUG_DRYRUN;
-  const static char str_debug_16[] PROGMEM = MSG_DEBUG_COMMUNICATION;
-  #if ENABLED(DEBUG_LEVELING_FEATURE)
-    const static char str_debug_32[] PROGMEM = MSG_DEBUG_LEVELING;
-  #endif
+  const static char str_debug_1[] PROGMEM = MSG_DEBUG_ECHO,
+                    str_debug_2[] PROGMEM = MSG_DEBUG_INFO,
+                    str_debug_4[] PROGMEM = MSG_DEBUG_ERRORS,
+                    str_debug_8[] PROGMEM = MSG_DEBUG_DRYRUN,
+                    str_debug_16[] PROGMEM = MSG_DEBUG_COMMUNICATION
+                    #if ENABLED(DEBUG_LEVELING_FEATURE)
+                      , str_debug_32[] PROGMEM = MSG_DEBUG_LEVELING
+                    #endif
+                    ;
 
   const static char* const debug_strings[] PROGMEM = {
     str_debug_1, str_debug_2, str_debug_4, str_debug_8, str_debug_16