Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f1/STM32F101/CAN1/ESR#0x0
error status register
EWGF
EPVF
BOFF
LEC
TEC
REC
https://github.com/modm-io/cmsis-svd-stm32