Tested myself this mission just now, (all patches loaded). After unodock you have mission path leading to trade lane and next to jump-hole leading to Tau (works good).
Can you please try load now mission save 38? (using any player made save, or autosave will not solve issues if there were some)How much missions you did in row (in row=without using load) for taking this issue above?
Hmm .. it looks your game files were not patched for some reason. I used your save, Horizon undocked and waypoint is set correctly (ss attached). Can you open m13sp.ini (Freelancer/data/Missions/M13) in notepad and check length and lines? .. I have 931034, lines: 34446