Do you own a Britax convertible?  If you’ve ever removed the harness from the seat to clean it or just for the heck of it (hey, why not, eh?), there may be a chance that you haven’t put it back on the seat properly.  What’s that you say?  It lines up straight, it’s not twisted, and it’s on the splitter plate just fine (the splitter plate is that metal T-shaped piece on the back of the seat that holds the harness ends).  But wait!  Perhaps the Velcro isn’t lining up with the cover any more.  Aha!