CAN FD on 6X STM32H7

I have tried following the instructions in NuttX CAN drivers on STM32H7x3 and ended up with the following observations when using cansend and candump:

  1. candump works for both classic CAN and CAN FD, but once candump terminates (I tested using -T option), it no longer runs (immediately terminates after giving the candump command)

Does anyone know what could be the issue?

One config parameter I did not set was CONFIG_NETDEV_IFINDEX=y as I could not figure out which setting in menuconfig sets it.