can SAM3X8E losing a frame

[autoprog]

Hi, I have a problem with losing 1 frame, on SAM3X8E
I get packets of 256 frames.
problem is the loss of 1 frame (eventually).

receive file
ex:
read(256)...ok
read(256)...ok
read(255)...bad <---cause the processing to stop
read(256)...ok

tried with con0.init() library
I tried direct mode can_init(CAN0, 84000000, bd).
send receiver ok, but sometimes miss 1 frame,
I use fifio buffer, I tried 2 types (fifo or Queue ).

I thought it might be CAN_BR =00142211, 500k /12xtal

if anyone has any new ideas.

thanks.