The only reason I know that post exists is because it does show up if I just go to https://lemmy.nz/ so i'm guessing it shows in the Subscribed Posts section, but if it isn't there then i'd be missing the post entirely I guess.
Whatever is happening, that post also doesn't seem to show on the home instance (when you visit https://sh.itjust.works/c/rugby) when sorting by new.
If you choose the sort type "Top week", it shows up fine on both lemmy.nz and sh.itjust.works
I'm not sure what the issue is but it doesn't seem to be specific to lemmy.nz. Maybe you could send a direct message to a mod and ask if they know what's up?
Being a cross post shouldn't matter. It's probably some weird lemmy issue, hopefully it will get solved over time. I'm not sure if there's much we can do in the meantime, but I suggested messaging a mod as they may have their own support community they can ask on.