CAN Bus issue with STM32F302

I am porting a code base that used to work well on the STM32F103 series.

The problem I have with the STM32F302VE seems to be related to the CAN FIFO's. What works:

1) CAN registers are working correctly

2) Initialization is executed normally

3) Receive interrupts are triggered when frames are on the bus

The problems I have are:

1) Can't read anything meaningful from the receive FIFO (RX data is all 0x00)

2) Attempt to transmit create a Hard Fault Error when the mailbox is written to

It looks like the FIFO are not enabled or not clocked. I cannot see anything specific to the CAN FIFO's beyond the enable and clock bit for the whole CAN subsystem.

Any idea?