Happened to me on a BMC, same issue.
I have professional, calibrated and fucking expensive torque wrenches, but I'm not willing to apply the advised Nm on delicate points like same clam, seatpost clamp and steerer any longer.
Torque the same clamp by hand and don't use force, you'll here it while riding on car it's too loose
Check shortlistings for a SL8 seatpost, a lot of people are seeking them cause they install a Darimo