This is getting old.
Sometimes, I'm not sure why, moving your camera around with rightclick cancels your casts. It seems particularly sensitive to up and down panning.
I'd love to post it on the bugtracker, but I can't find the wowhead ID for camera up and down panning and even if I could, I still cannot access the bugtracker, since it's an insecure website. It spamredirects me.