working debug items for delta homing issue.

* merged in changes in bug fixes since they all make sense
* merged in head since fixing types makes sense as well
* still looking into how to address MarlinFirmware#11676 -
confirmed code location of errors with homing

Marlin/Configuration.h

@@ -749,7 +749,7 @@
   //#define ENDSTOPPULLUP_XMIN
   //#define ENDSTOPPULLUP_YMIN
   //#define ENDSTOPPULLUP_ZMIN
-  //#define ENDSTOPPULLUP_ZMIN_PROBE
+  #define ENDSTOPPULLUP_ZMIN_PROBE
 #endif
 
 // Enable pulldown for all endstops to prevent a floating state
@@ -823,7 +823,7 @@
  *
  * :[2,3,4,5,6,7]
  */
-//#define ENDSTOP_NOISE_THRESHOLD 2
+#define ENDSTOP_NOISE_THRESHOLD 2
 
 //=============================================================================
 //============================== Movement Settings ============================
@@ -1376,8 +1376,8 @@
   #define AUTO_BED_LEVELING_3POINT
 #else
 //#define AUTO_BED_LEVELING_LINEAR
-#define AUTO_BED_LEVELING_BILINEAR
-//#define AUTO_BED_LEVELING_UBL
+//#define AUTO_BED_LEVELING_BILINEAR
+#define AUTO_BED_LEVELING_UBL
 //#define MESH_BED_LEVELING
 #endif
 
@@ -1392,7 +1392,7 @@
  * Turn on with the command 'M111 S32'.
  * NOTE: Requires a lot of PROGMEM!
  */
-//#define DEBUG_LEVELING_FEATURE
+#define DEBUG_LEVELING_FEATURE
 
 #if ANY(MESH_BED_LEVELING, AUTO_BED_LEVELING_BILINEAR, AUTO_BED_LEVELING_UBL)
   // Gradually reduce leveling correction until a set height is reached,

Marlin/src/module/delta.cpp

@@ -235,7 +235,13 @@ void forward_kinematics_DELTA(const float &z1, const float &z2, const float &z3)
 void home_delta() {
   if (DEBUGGING(LEVELING)) DEBUG_POS(">>> home_delta", current_position);
   // Init the current position of all carriages to 0,0,0
-  current_position.reset();
+  // if we know where we are, do not throw away our current_position
+  if (!all_axes_known()) {
+    current_position.reset();
+  } else {
+    if (DEBUGGING(LEVELING)) DEBUG_POS(">>> home_delta.no_dumb.reset()", current_position);
+    //current_position.reset();
+  }
   destination.reset();
   sync_plan_position();
 
@@ -254,6 +260,7 @@ void home_delta() {
       - probe.offset.z
     #endif
   );
+  if (DEBUGGING(LEVELING)) DEBUG_POS(">>> home_delta.line_to_current_position()", current_position);
   line_to_current_position(homing_feedrate(Z_AXIS));
   planner.synchronize();