Mine had a strong detent when it first arrived. It took several hundred flips before it got better. Like @JAB stated, some of them are strong and the 456 has been the worst.
Don't know how much good putting a drop of oil will help, but it doesn't hurt to try. You can also back off the pivot screw a tad to see if that helps. Eventually it does get better, you just have to give your finger a rest and let it get over the soreness. I had to alternate with both hands to give my finger a rest.