Are you sure this is not an electrical fault (like voltage
dropping out momentarily)? I've experienced dropouts
as well, never figured out why (for lack of chasing). The
automotive power environment is ugly at best. Wonder
if some local filtering on the OBDII 5V line might help.
It would not be a bad idea to try a limited PID set that
puts you into max frame rate, just to see. My gut feel
as I recall was that disconnects happened when there
was "a lot of stuff going on" and maybe the bus is just
too chaotic, or something.