I'm trying to book a multi-city trip via Aeroplan and keep having SQ flights show up that, when push comes to shove, are unbookable:

YVR-SYD (direct Air Canada)
SYD-MLE via SIN (Singapore Airlines)
MLE-YVR via DEL (Air India / Air Canada)

That middle leg keeps showing up, but even the agents at the call centre can't book it (even trying as a one-way). The said that happens often with SQ, that flights will show up but then won't be available. . . It's bad enough they hold their first class for their own, but to keep getting my hopes up showing me flights that then aren't ticketable is a pain!