Playback Won't Shutup!

The CAN hardware does tend to default to "send until ACK" so if nothing is setting the ACK bit it will continue to send forever. On a populated CAN bus this is usually OK as there won't be too many resending attempts before the message successfully transfers and is ACK'd. But, it is not always idea. It is possible to put the hardware into "send once and give up" mode. This is usually what a car ECU will do so that a failure in the bus doesn't immediately saturate the bus with re-attempts. I think I ought to add support to SavvyCAN to set the desired transfer mode at the hardware level. Some hardware can also do three attempts and give up. The ESP32 can do this I think. The MCP2517FD can do it for sure. That's the ideal setting for most things. If it fails once it might be an arbitration failure. If it fails to send three times in a row it's probably a bus misconfiguration and it might as well give up.