STOP2 Low Power Mode in STM32WB55

[ABN]

Hello,

I'm using a custom board which has STM32WB55 as the MCU. For the application, requires the MCU in sleep mode. The chosen sleep mode is STOP2. I referred the example project 'PWR_STOP2_RTC' which is available for the p-nucleo board and tried to replicate the same for my custom board. 
After testing for power consumption, the custom board is taking around 300uA as opposed to ~3uA per datasheet.
Can anyone point to me why there is extra consumption, and if there is any more config to be done in the cubeMx or in the code.

Thank you in advance.

[ABN]

@Remy ISSALYS @Remi QUINTIN can you guide me through the low power design phase.?? This is becoming critical and it is blocking the use of Low Power modes in our application. 

Attaching the schematics and the main.c file for reference.