I'm new to AC, so please be kind. I've searched FT and come up empty.

I'm having a problem with the booking engine dropping the final leg on a reservation when it gets to the point of selecting seats. I've been working on getting rt BOS-ITM. The routing I've selected is BOS-YYZ-NRT-ITM and ITM-NRT-YUL-BOS. It's only when I get to the seat selection screen does the final leg YUL-BOS drop off. Seat selection shows only five flights (1/5 to 5/5). Then moving onto the payment screen, the itinerary shows only five flights. Needless to say, I've not completed the purchase. All my usual work arounds for this type of issue (e.g., multi-city searches, etc) that I use on other websites don't work.

Any suggestions are appreciated.