If the calipers are mounted on the wrong side - which is entirely possible - it follows from the dual circuit design that it will be impossibe to get rid of all air in the system. To get all the air out, the bleeder nipples need to be at the highest points of their respective circuits. Which is the case for, say, the top left caliper. But if this caliper is mounted upside down, on the right hand side of the car, nipple #2 will be lower than the two channels it serves. And air will be trapped inside. If this is indeed your problem, you are not the first to have done this. And you will not be the last.