To the moderator,
moving this thread to online booking tool bug thread ?
I have simllar problem about ex-JNB DONE4 online booking a few days ago.
A simple itin such as JNB-HKG-YYZ-LHR-JNB quotes 48040 ZAR base fare.
However adding some side trip (not sure, which part caused this),
such as JNB-HKG-HND-SIN-HND-HKG-YYZ-LHR-DXB-LHR-JNB quotes
96080 ZAR base fare.
I am afraid of ex-JNB fare rising (just a speculation),
so made a booking of a simple itin, and am going to change that with a fee.