this is not a direwolf issue. this is an issue with the ax0 N_KISS line dicipline for tty/pty's of the linux kernel. indeed. first packet -after you bring an ax0 interface up- has KISS control byte 80 (data packet channel 8), second has KISS control byte 20 (data packet, channel 2). any packet following that is fine. bug should therefore be fixed in the ax25 protocol stack of the linux kernel (mainly the part that handles kiss and ax0 type interfaces) and not in direwolf. it happens wether you use it for direwolf or not. comes out of the interface itself (either that or something very weird is going on with the pty most people would use to create a fake serial line.
just spent an hour tracing down where these wrong bytes came from as well.
probably does the same thing on a real ttyS0 serial port as it does on the pty. didn't test that. people with a real tnc on a real serial port would never notice 2 packets going missing anyway. at most it'd blink a led. none of em would have 8 or even 3 channels ;P
note that the time at which this problem occurs is the first 2 packets after -creating- and -bringing up- the ax0 device. (and only then). you can close the tcp socket to direwolf (or anything kiss-tcp), restart direwolf as a whole and let it reconnect, etc. as long as that ax0 interface stays there, the problem will not re-occur.