#define CONFIGURATION_H

I wonder if it is something I have messed up in the firmware config file (I used both #define BLUETOOTH_SERIAL 2 (as well as -1) and I have changed "bluetoothSerial": 2 in the connection str

#define FILAMENTCHANGE_X_POS 0

 #define  WRITE(IO, v)   _WRITE(IO, v)

  #define  MASK(PIN)    (1 << PIN)

 #define SDCARDDETECT -1

Add#define COOLER_PWM_SPEED 2

#define ENDSTOP_X_BACK_MOVE 5

if using dev version you could also test #define REDUCE_ON_SMALL_SEGMENTS

Here's a link to the new commands & syntax:  https://github.com/MarlinFirmware/Marlin/tree/devel-ubl#duplicate=0

#define SERVO0_NEUTRAL_POS 1450

#define Z_PROBE_X1 0

   #define MACHINE_NAME CUSTOM_MENDEL_NAME

// #################### Z-Probing ##################### #define Z_PROBE_Z_OFFSET 0.2 #define Z_PROBE_Z_OFFSET_MODE 0 #define UI_BED_COATING 1 #define FEATURE_Z_PROBE 1 #define Z_PROBE_BED_DISTA

#define ZHOME_X_POS 110

#define Z_PROBE_SWITCHING_DISTANCE 1  <<<<<<set this to 3,to raise probe a bit more to untriger between probes

#define Z_PROBE_SWITCHING_DISTANCE 1 <<<<<<set this to 3,to raise probe a bit more to untriger between probes

#define Z_PROBE_HEIGHT 0.1            this is distance nozzle to bed when probe triggers

#define Z_PROBE_Z_OFFSET 0

 #define  _WRITE(IO, v)   do { if (v) {DIO ##  IO ## _WPORT |= MASK(DIO ## IO ## _PIN); } else {DIO ##  IO ## _WPORT &= ~MASK(DIO ## IO ## _PIN); }; } while (0)