Hmm. Can't see the 2 bolt clamp, but is one of them a bolt for tightening a shim because the post is not the same diameter as the seat tube?
If it started happening after customer pushed the seatpost lower, I'd raise it back up and try it. Maybe it's too low and binding down in the seat tube, or if internal dropper the cable end is messed up or hitting something down in the tube.
They do say not to over tighten, but has to be tight enough.