I am very confused by this. I am trying to price out the following Multi-City itinerary on the website (dates are a bit different than what I want, but I can reproduce the same issue with these dates):

30Dec YVR-TPE
05Jan HND-YYZ

If I select the direct AC YVR-TPE flight on the 30th, the website is ONLY offering me economy fares for the HND-YYZ flight. (I am trying to price out PE legs for both). If I select one of the connecting flights option for the outgoing (which are a lot more expensive), then I get the options for PE and J on the return. Is there something about the fares on the YVR-TPE direct that won't allow me to combine it with the HND-YYZ return in something other than economy? (I find that very strange - I could perhaps understand if it gave me a price that was close to full-fare, but it's not offering an option at all!).

Website glitch or fare combination restriction?