Update: During a recent test-run I had both of the two CAN interfaces of my RPI4 Model B fail. First can0
and then some hours later can1.

Furthermore I attached another dump after fail. The last one was for the case where my application
receives 4 wrong messages (2 of them equal). This case is where my application receives
2 wrong messages only (both being equal). The candump has a different pattern:

CAN selftest can1 ......idx    2 tx:2A5#00 02 01 08 9A 5D 15 4B
         rx:2A5#00 00 D1 7D 9D 18 91 50
idx    3 tx:2A5#00 03 AC 4D 55 BF 2F 56
         rx:2A5#00 00 D1 7D 9D 18 91 50
c (584) fail
0: RX72 (004/003)  2A5#00 00 D1 7D 9D 18 91 50
0: RX72 (004/002)  2A5#00 00 D1 7D 9D 18 91 50
0: TX72 (003/002)  2A5#00 03 AC 4D 55 BF 2F 56
0: RX72 (003/001)  2A5#00 01 B0 ED 22 AE 94 9F
0: TX72 (002/001)  2A5#00 02 01 08 9A 5D 15 4B
0: RX72 (002/000)  2A5#00 00 57 3D 14 2B 3A BA
0: TX72 (001/000)  2A5#00 01 B0 ED 22 AE 94 9F
0: TX72 (000/000)  2A5#00 00 57 3D 14 2B 3A BA

  can1  2A5  [08]  00 03 1C 48 53 3D E1 9B
  can1  2A5  [08]  00 03 1C 48 53 3D E1 9B
  can1  2A5  [08]  00 00 57 3D 14 2B 3A BA
  can1  2A5  [08]  00 00 57 3D 14 2B 3A BA
  can1  2A5  [08]  00 01 B0 ED 22 AE 94 9F
  can1  2A5  [08]  00 01 B0 ED 22 AE 94 9F
  can1  2A5  [08]  00 02 01 08 9A 5D 15 4B     **
  can1  2A5  [08]  00 02 01 08 9A 5D 15 4B     **
  can1  2A5  [08]  00 02 01 08 9A 5D 15 4B     **
  can1  2A5  [08]  00 02 01 08 9A 5D 15 4B     **
  can1  2A5  [08]  00 03 AC 4D 55 BF 2F 56     **
  can1  2A5  [08]  00 03 AC 4D 55 BF 2F 56     **
  can1  2A5  [08]  00 03 AC 4D 55 BF 2F 56     **
  can1  2A5  [08]  00 03 AC 4D 55 BF 2F 56     **

I've seen other failures that followed those two pattern. Unfortunately, I removed my external logger, so
it's unsure what actually happens on the bus.

> And one more observation: Once or twice I have seen my application fail with not returning MTU size in the socketcan read:
>   ERROR: recvfrom: ret=16, errno=0
> Is there any obvious explanation for this? I tried to add more output for this case, but it has not happed until then.

Stupid me. Obviously this is a message in old CAN_MTU size. Is this still used for errors even if the MTU is set to CANFD_MTU?
This did not show up again, so I wasn't yet able to look into the data payload.

-- Stefan