hi
i'm new to routings ex SA and having read the OW Rules I thought that this routing was possible .... I've given the bare bones - the area of contention is at the end

JNB-HKG-SYD-WLG-SYD-HKG-JFK-LAX-LHRxNBO-LHR-JNB

The online booking tool doesn't let me do the final flights via LHR - says only allowed one intercontinental arrival and departure
I thought that this routing was possible as long as one of the 2 LHR visits was transit only
Or have I not understood the rules correctly

Thanks!