Sometimes a message posted on a mailbox is lost; the rx thread receives the vary last mesage but not the previous. It seems that if the RX task is waiting when the TX task send the message all is ok but if the RX task is interrupted during a os_mbx_wait processing by the TX task then the RX task exits the os_mbx_wait with the last message posted skipping the ones already in the mailbox (messages lost and FIFO not respectd). Has anyone seen the same problem? Thank all for answers.