I end up with a similar problem if the saddle is too wide just forward of the sit-bones. My solution is to remold the saddle shape just a bit by playing a heatgun to the underside of the saddle and squeezing the plastic narrower, usually over several sessions, until it feels just right. I only need to do this to one side due to some sort of asymmetry in my anatomy. I also find it helpful to point the saddle a small amount to one side instead of perfectly straight ahead.