Problems with a slipping seatpost
Your local bike shop should be able to sell you some carbon gripping compound, for example Finish Line Fiber Grip.  Other similar brands are available!

I've no idea what the seatpost clamp is on your bike but I'm always suspicious of ones that are hand tightened.  I have 2 bikes with carbon seatposts &amp; Ali frames, I use Salsa clamps that require an allen key &amp; I don't experience any slippage.