I have this problem with my hardtail MTB, especially on a rough trail ride. Fortunately it has a removable seatpost clamp, so I purchased some extras that have a heavier clamp bolt. They are unbranded but look at lot like what origin8 has always sold. This works better, and I have spares. My next option is to just try a different post, but I haven't taken the time to find a long enough one and I'm not going to pay over $100 for new one. That might be your best option if you have an integrated post clamp.