Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32wb0/STM32WB06/RADIO/LR_PD_THR_DIG_ENG#0x0
LR_PD_THR_DIG_ENG register
preamble detect threshold value
https://github.com/modm-io/cmsis-svd-stm32