The seatpost clamp on the LCR018 isn’t the best solution, and there is too much play between the seatpost and the frame. However, as others have said, seatpost slippage — unfortunately — is a common problem on many bikes. My Cube has about the same issue.
My solution:
I wrapped TESA electrical tape (2–3 layers) around the very end of the seatpost and the same further up near the clamp (once the height was roughly set). This way, the post fits tightly and even has to be pushed down into the frame.
With post diameter increased by two wraps of tape, carbon paste, and the clamp tightened to 10 Nm, there is no slipping and no movement.
PS: i do this on many bikes. Because it also prevents/lowers water ingress into the frame