I've got a Rock Lobster 853 that had slippage issues from new.
Had the post and frame measured - slightly loose, but within limits according to my lbs.
Merlin provided a new, custom made Hope clamp and a Thomson post in an attempt to cure the issue, neither of which worked.
Took the bike back half a dozen times, but Merlin said there was nothing wrong.
They test rode it and said they couldn't replicate the problem, but it still slipped when I used it.
Eventually gave up as they blamed me for not knowing how to do up a qr.
But the post still slipped, even after being tightened by them.
Carbon paste helped a little but didn't cure it.
Eventually bought an On-One qr, which solved the problem immediately.
Hope qr's are appalling:
They don't work properly, then they break.