Whoa! You got me ... :thinking:
Just thinking out loud ... maybe it has something to do with whether the number of sts divided by 2 is an even or odd number?? I think that might effect the k2 p2 rib? If the divided number is odd, you can't just do k2p2 through and through. You can only do k2p2 on every other row. The rows in between have to start w/ p2k2. I'm not sure that would account for the RS looking wrong.
Any chance that you have a pic??