Being directional suggests there is something different about each end plug.
Ethernet itself works with 4 sets of cable pairs, and i know from experience that if one connection is bad, the cable can still work just not optimally (dont ask me which pin, but i had a bad connection on a diy wall socket which only gave me 100mb connection. I remade the socket again and the green light on the switch confirmed 1000mb connection was now working).
Assuming that all 8 wires are connected at both ends. If thats the case, then directionality can only come from another difference. Perhaps grounding of one plug?