I have a 16 segment ex-JNB itinerary DONE5 booked and priced which includes MH92 KUL-LAX in D. It prices beautifully.
CPT-LHR (transfer only)-HEL-MAD-LHR-SYD-NRT-DEL-KUL-LAX-DFW-BOS-MIA-SEA-ORD-DOH-CPT
However, when I try to do the reverse (LAX-NRT-KUL, MH93), it will not allow me anything but L class. This is despite there being D class available. I have tried dates in January, February and March, all which have D availability in ExpertFlyer, but won't allow me an D seat on the flight.
Is it a bug, or have I fallen foul of some rule? I can't seem to find a rule that covers this issue.