Not sure about the swivel knife problem without seeing you carve. If the knife is sharp, you shouldn't have any of these problems with cased leather. You might want to watch some videos on Youtube and Tandy and watch how other folks use their swivel knives, I suspect you may not be tilting it forward so that you're cutting with the tip and as far as one side having a ridge or being differenet than the other, I suspect you may not be keeping the swivel knife perpendicular to the cutting surface. Like I said, hard to tell without seeing it happen, check out some videos and watch how they tilt the knife forward and pull it effortlessly through the leather while keeping it straight from side to side, hard to explain better to watch it.
Hope that helps,
Ken