Ah yeah, that's a Tickets + XenBase issue. I could've sworn I fixed that a while ago now. IIRC it only affects discussion view so if you switch to simplified view, that should sort it temporarily. Kind of the reason I actually added that since it's pretty tricky to use XenForo's default discussion layout for anything other than threads / posts and maintain third-party style compatibility.
Leave it with me and I'll see what I can do about it.