Merge pull request #3707 from thinkyhead/rc_fix_delta_blocking_move

Fix dipping on DELTA robots during G29

Marlin/Marlin_main.cpp

 #if ENABLED(AUTO_BED_LEVELING_FEATURE)
   int xy_travel_speed = XY_TRAVEL_SPEED;
   float zprobe_zoffset = Z_PROBE_OFFSET_FROM_EXTRUDER;
+  bool bed_leveling_in_progress = false;
 #endif
 
 #if ENABLED(Z_DUAL_ENDSTOPS) && DISABLED(DELTA)
       destination[X_AXIS] = x;
       destination[Y_AXIS] = y;
       destination[Z_AXIS] = z;
-      prepare_move_raw(); // this will also set_current_to_destination
+
+      if (x == current_position[X_AXIS] && y == current_position[Y_AXIS])
+        prepare_move_raw(); // this will also set_current_to_destination
+      else
+        prepare_move();     // this will also set_current_to_destination
+
       stepper.synchronize();
 
     #else
 
     feedrate = homing_feedrate[Z_AXIS];
 
+    bed_leveling_in_progress = true;
+
     #if ENABLED(AUTO_BED_LEVELING_GRID)
 
       // probe at the points of a lattice grid
       stepper.synchronize();
     #endif
 
-    KEEPALIVE_STATE(IN_HANDLER);
-
     #if ENABLED(DEBUG_LEVELING_FEATURE)
       if (DEBUGGING(LEVELING)) {
         SERIAL_ECHOLNPGM("<<< gcode_G29");
       }
     #endif
 
+    bed_leveling_in_progress = false;
+
     report_current_position();
+
+    KEEPALIVE_STATE(IN_HANDLER);
   }
 
   #if DISABLED(Z_PROBE_SLED) // could be avoided
       calculate_delta(target);
 
       #if ENABLED(AUTO_BED_LEVELING_FEATURE)
-        adjust_delta(target);
+        if (!bed_leveling_in_progress) adjust_delta(target);
       #endif
 
       //DEBUG_POS("prepare_move_delta", target);