Sounds like a Lyman mould that was cut with their worn-out double acting vise. Look at the top of the mould with the sprue plate open, if the block half to the left is "away" from the block on the right, like the clockwise-turning cherry torqued the left away from the handles and the right back toward the handles, this is what happened. I've fixed a few of them by shifting the alignment holes (peening metal on one side of the hole and needle-filing it away from the other side) and lapping, others just lapping trues it up well enough. The problem with lapping is getting each cavity exactly the same, which is just about impossible and takes a few attempts just to get close. Like FB said, it's not critical on low-velocity bullets, so as long as the bullets seal the bore and don't lead, easiest thing is just to live with it and use them as-is. If it bothers you, maybe try to correct it, but it isn't difficult to ruin the mould trying to fix it. Only you can determine what your time is worth. For me, it's a better option to order a new mould from Accurate that's round and the size I want rather than waste hours and hours trying to fix a defective one.