Firstly - this is crazy - because it can really mess up some fares which have a limit on "transfers" as now an extra transfer may be required for some routes.
Second - I wonder if the other flights in the Amadeus systems which run multiple stops with the same flight number basically don't board any local passengers at the mid-point and thus can make it work. It's all a bit strange that this is not possible. . . For example - LX 294 is a circle trip ZRH-NBO-DAR-ZRH.
how can that one be handled but somehow AC can't do GVA-YUL-YYZ??